Gorums release v0.7.0

Gorums release v0.6.1

Gorums release v0.6.0

Gorums release v0.5.0

Gorums release v0.4.0

Merge pull request #123 from relab/revised-user-guide

Revised user guide and other docs

Remove the `grpc.CallOption` field from ordered RPCs

The field was not actually used for anything.
Removing it required some changes to the template variables though, as
one-way calls and RPCs do not have the same dependencies.

Fixed warnings reported by golint

Added some missing comments to exported symbols
Renamed tests/message_encoding to tests/encoding
As well as other minor cleanups

added benchmark for the receiveQueue

To run this benchmark:
go test -bench=BenchmarkReceiveQueue

Results on my machine are pretty conclusive:
BenchmarkReceiveQueue/RWMutexMap-12                 13286848                77.7 ns/op
BenchmarkReceiveQueue/syncMapStruct-12               2467936               482 ns/op
BenchmarkReceiveQueue/syncMapDirect-12               2494368               485 ns/op

gorums: changes for v0.1.0-gogo

This is in preparation for tagging a release branch so that it can
easily be referenced in the future, when the new version becomes
master.