documentation for some of the builtins
references #18
Style fixes.
Merge branch 'master' into pr/222
Jank @olasd's hack, clean up core.

 The core shall from now on be only for the core language bits. Macro
 bits shall live in hy.macros and in hy.compiler. This cleans up
 garbage.
Don't leave cruft around in sys.modules when an import fails.

Closes: #214, #225

Squashed from a bunch of commits by @olasd
Fix flake error
Adding NEWS entry
Add emacs backup files and rope project dir to .gitignore