Fix Snapshots (#122)

#120 has a bug where the `Snapshot` only
includes the subscopes and not the metrics on the current scope. This fixes the
`snapshot` method to include metrics on the current scope as well.

Add TestScope (#120)

This commit plucks select changes from #69 and #43
to bring uber-java/tally on par with uber-go/tally.

It adds a `TestScope` class which allows users of the library to get a
`Snapshot` of all the metrics emitted by the scope. Users can then assert if
certain metrics were created.

Define a custom Scope Key for reducing memory allocations (#116)

* save progress

* revert to master

* sync with master

* add gradle files

* gradle cleanup

* add unit tests and cleanup code

* self review

* self review

* review comments address

* fix flaky test as pointed in review

* add benchmark

* self review

* nit pick

Check scope existence lock free first (#110)

Release 0.11.1 - fix checkstyle (#101)

Merge pull request #100 from alexeykudinkin/rel

Release v0.11

Release v0.11

Release 0.10.0 (#89)

Merge pull request #84 from alexeykudinkin/mp-ff-rel

Release 0.9.1

Upgrade to version 0.5.3 (#60)