Propagate connection initialization problems

When connection failed to open, it used to not tell it to the caller.
With this patch it propagates the error to the caller (like it used to
be in 0.2), and closes the orphaned connections (which is a new
feature).

This patch also makes basic tests pass again.
Travis-ci support

travis-ci requires different credentials than we have by default,
therefore a conditional for credentials in tests was introduced.
Merge pull request #90 from Motiejus/travis

Enable travis-ci
Allow passing start_cmds from environment
Merge pull request #91 from Motiejus/arbitrary_cmds2

Allow passing start_cmds from environment