Add Travis CI tests for go-raft.

In playing around with the code in go-raft, I noticed that a number
of the tests are non-deterministic.  I figure Travis CI integration
will help illuminate changes that introduce regressions against
test health.
Merge pull request #92 from coreos/master

fix log_entry.go
Merge pull request #93 from coreos/master

sleep time should not be hardcoded
Merge pull request #91 from matttproud/feature/testing/continuous-integration

Add Travis CI tests for go-raft.
should not close request body