Housekeeping: drop dead code and fix stale docs

[bbatsov]

A few small cleanups I found while auditing the repo:

• Removed suitable.compliment.sources.cljs.ast, an orphaned byte-for-byte copy of suitable.ast that nothing required.
• Fixed the 0.6.2 changelog entry - it was dated 2033 and used an h1 heading where every other version uses h2.
• Swapped the dead versions.deps.co downloads badge for the Clojars one.

No behavior change, so no tests.

• The commits are consistent with the contribution guidelines
• You've added tests to cover your change(s) (N/A - docs and dead code only)
• All tests are passing
• The new code is not generating reflection warnings
• You've updated the changelog (if adding/changing user-visible functionality)