Fixed issue where pre-install script would attempt to copy to a non-e…

…xistent directory.

Add interface for heap to support Reverse for `order by desc`

Update CHANGELOG

Tweak Support sectioning

[ci skip]

Backport PR4179 to 0.9.4.

Fix race in cluster RPC serialization

Point was accessed from multiple goroutines and there was a race on the the internal
cachedFields and cachedName fields.  Accessing these fields is unnecessary work as it
requires the point to be unmarshal into Go types and then remarshaled back into protbuf
types.  Instead, just send the line protocol version already available on the point via
the protobuf.  This avoid accesssing these cached fields and eliminates some extra work.

Possible fix for influxdata#4069

0.9.4 is out

[ci skip]

Merge pull request influxdata#4072 from influxdb/wal_stats

Add stats for the WAL

Fix deadlock in metastore

The interaction of continuous query service, the meta-store loading
and initializing raft state, and syncing node info could cause a
deadlock in some instances.  There was an extra read-lock taken by isLeader()
when it already had a read-lock.  Removing this extra lock fixes the startup
deadlock.

Fixes influxdata#3607

Fix metafile so it doesn't get trampled by other goroutines.

Fixes influxdata#3832 and fixes influxdata#3833