Babel 6

Now using Babel 6!

Much long-awaited upgrade makes documentation.js compatible with fresh
new Babel-using codebases.

And also:

• GitHub Enterprise support
• New tag support: abstract, override, readonly, interface, variation, see, todo
  (only in parsing phase, not yet in all outputs)
• Parses jsx and es6 extensions by default, as well as .js
• Fixes polyglot mode
• Now shows the @throws tag content in Markdown output
• Support for example captions