Parse forwarded messages
Counter forwarding

Gost now supports forwarding metrics to another gost for global
aggregation.

Fixes #16.
Sampling is only for counters
Rename BufferedCounts to the more accurate BufferedStats
Don't need a receiver for gocheck methods
Move stats testing to a new buffered stats unit test
Some test updates
Add notes on forwarding and tuning to the README

Also general readme cleanup.
Test for checking that forwarding doesn't happen when disabled