travis: install protobuf-compiler.
Merge pull request #37 from m1ch1/master

travis: install protobuf-compiler.
Add FileUtils.

Add utility methods to atomically write an integer to a file and
to read the integer back from the file. These methods are meant
to be used to read and write epoch files.
Merge pull request #38 from m1ch1/atomic

Implement atomic file for proposed / acknowledged epoch files
Leader election implementation.