log, vendor: vendor in log15 inline into our codebase

log/CONTRIBUTORS

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+Contributors to log15:
+
+- Aaron L 
+- Alan Shreve 
+- Chris Hines 
+- Ciaran Downey 
+- Dmitry Chestnykh 
+- Evan Shaw 
+- Péter Szilágyi 
+- Trevor Gattis 
+- Vincent Vanackere 

log/LICENSE

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+Copyright 2014 Alan Shreve
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+   http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.

log/README.md

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+![obligatory xkcd](http://imgs.xkcd.com/comics/standards.png)
+
+# log15 [![godoc reference](https://godoc.org/github.com/inconshreveable/log15?status.png)](https://godoc.org/github.com/inconshreveable/log15) [![Build Status](https://travis-ci.org/inconshreveable/log15.svg?branch=master)](https://travis-ci.org/inconshreveable/log15)
+
+Package log15 provides an opinionated, simple toolkit for best-practice logging in Go (golang) that is both human and machine readable. It is modeled after the Go standard library's [`io`](http://golang.org/pkg/io/) and [`net/http`](http://golang.org/pkg/net/http/) packages and is an alternative to the standard library's [`log`](http://golang.org/pkg/log/) package.
+
+## Features
+- A simple, easy-to-understand API
+- Promotes structured logging by encouraging use of key/value pairs
+- Child loggers which inherit and add their own private context
+- Lazy evaluation of expensive operations
+- Simple Handler interface allowing for construction of flexible, custom logging configurations with a tiny API.
+- Color terminal support
+- Built-in support for logging to files, streams, syslog, and the network
+- Support for forking records to multiple handlers, buffering records for output, failing over from failed handler writes, + more
+
+## Versioning
+The API of the master branch of log15 should always be considered unstable. If you want to rely on a stable API,
+you must vendor the library.
+
+## Importing
+
+```go
+import log "github.com/inconshreveable/log15"
+```
+
+## Examples
+
+```go
+// all loggers can have key/value context
+srvlog := log.New("module", "app/server")
+
+// all log messages can have key/value context
+srvlog.Warn("abnormal conn rate", "rate", curRate, "low", lowRate, "high", highRate)
+
+// child loggers with inherited context
+connlog := srvlog.New("raddr", c.RemoteAddr())
+connlog.Info("connection open")
+
+// lazy evaluation
+connlog.Debug("ping remote", "latency", log.Lazy{pingRemote})
+
+// flexible configuration
+srvlog.SetHandler(log.MultiHandler(
+    log.StreamHandler(os.Stderr, log.LogfmtFormat()),
+    log.LvlFilterHandler(
+        log.LvlError,
+        log.Must.FileHandler("errors.json", log.JsonFormat()))))
+```
+
+Will result in output that looks like this:
+
+```
+WARN[06-17|21:58:10] abnormal conn rate                       module=app/server rate=0.500 low=0.100 high=0.800
+INFO[06-17|21:58:10] connection open                          module=app/server raddr=10.0.0.1
+```
+
+## Breaking API Changes
+The following commits broke API stability. This reference is intended to help you understand the consequences of updating to a newer version
+of log15.
+
+- 57a084d014d4150152b19e4e531399a7145d1540 - Added a `Get()` method to the `Logger` interface to retrieve the current handler
+- 93404652ee366648fa622b64d1e2b67d75a3094a - `Record` field `Call` changed to `stack.Call` with switch to `github.com/go-stack/stack`
+- a5e7613673c73281f58e15a87d2cf0cf111e8152 - Restored `syslog.Priority` argument to the `SyslogXxx` handler constructors
+
+## FAQ
+
+### The varargs style is brittle and error prone! Can I have type safety please?
+Yes. Use `log.Ctx`:
+
+```go
+srvlog := log.New(log.Ctx{"module": "app/server"})
+srvlog.Warn("abnormal conn rate", log.Ctx{"rate": curRate, "low": lowRate, "high": highRate})
+```
+
+## License
+Apache

log/README_ETHEREUM.md

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+This package is a fork of https://github.com/inconshreveable/log15, with some
+minor modifications required by the go-ethereum codebase:
+
+ * Support for log level `trace`