removed binary example_executor, added to .gitignore.
Merge pull request #18 from vladimirvivien/pure

removed binary example_executor, added to .gitignore.
Merge branch 'pure' of github.com:mesos/mesos-go into pure
Updated godep

Replaced mesosphere/testify with stretchr/testify.
Modified debugging messages.
Added Executor.Disconnected().
Added stopped field in executor driver.
Removed locks in sendStatusUpdate and sendFrameworkMessage to avoid deadlock.

Working on a way to serialize events.
added tests for http_transporter, split upid tests.
Merge pull request #21 from vladimirvivien/pure

added tests for http_transporter, split upid tests.
Fixed data race in messenger.Start() and messenger.Send()

Move the listening logic into transporter.Listen(). So that
we can make sure that messenger.Send() is called only after
the tranporter.upid is ready.