Fix bug with block quote split over two paragraphs and an abutting paragraph at the start.

Closes #96

i.e. this case:

    a
    > b

    > c
Add JSHint support.

Use `npm run check` or `npm run lint`.
Fix a few JSHint warnings.
.jshint.rc: Enable curly rule.
Get rid of node.js v0.9 from travis; it was buggy and not stable.
Reindent markdown.js.