Improve test coverage

[langston-barrett]

Brainstorm other things to test. Immediately:

• Prompt manipulation
• A test for every function

There are also just some outdated tests. init is no longer supported, only sourcing and in.

Additionally, it looks like Travis can report success even when some tests fail. This needs to be investigated.

Tests also leave unncessary bin/ symlink to .godeps/bin. This should be removed by gvp out if it isn't, and if it is, the tests should use it. This might take another ticket.