Merge pull request #11 from darinmorrison/master

Add minimal README.md
Fix prettyprinting (details below)

* Generate names for variables
* Do it in a monad
* Fix bugs with bound variable numbering in printer (whoops)
Remove unused function
Layout cleanup
Merge pull request #12 from jonsterling/fresh-pretty

Fix prettyprinting (details below)
Add .travis.yml
Unfreeze dependencies
Actually, never mind that. I'm going to freeze it.

I don't have GHC 7.6, and I don't actually think it's terribly important
that we support it. Anyone who has 7.6 who wants to take ownership of
making things build for 7.6 can do so, but it's utter insanity to not
freeze one's dependencies (even during development) if "reproducible
builds" is at all a desired property.

By that token, I'm only targeting 7.8 on travis; if someone wants to
figure out how to freeze a different set of dependencies for 7.6 and
hook that up with travis, they are welcome to.
Started on some informal documentation of the judgments
Remove errant bracket
Add another rule
Change notation to be more in-line with Bauer/Stone
Add a command-line user interface
Document CLI commands in README.md
Merge pull request #15 from darinmorrison/feature/cli

Add a simple command-line user interface
Add note to README about versions of GHC/cabal
Remove some dead code
Fix order of arguments in Id constructor (close #8)
Update the typing rules document w/ bidirectionality, more rules