Trivial tweaks to README
Simplify implementation of if-let and when-let with define-simple-macro
Ignore "compiled" directory
Merge pull request #9 from qerub/misc

Miscellaneous tweaks
Add .DS_Store and change compiled to compiled/
Use Travis CI
raco link rackjure

Tests need rackjure linked as a collection.
Add (define collection 'multi) for Racket 5.3.6
Use `language: c` in .travis.yml
Test on Racket 5.2, too.

Note: Someone pointed out that multiple `env` items in `.travis.yml`
should result in a build matrix. So I want to try that out. Also,
commit 8e31e4a7ea for issue #5 was intended to make this work on 5.2,
so, let's test for that version in particular.

Obviously I'm trying all this on a topic branch. May or may not merge
to master.
Add THANKS.md
Rewrite the applicable dicts section of README.md
Add Racket 5.3.6 to Travis CI test matrix.
Prose edit re older versions of Racket.