Improve indentation.

- Consider continued lines.
- Consider multi line string.
- Consider multiple opening/closing parens in previous line.
- Allow customization of some features.
Merge branch 'indent'

Fix typo.
Add filetype plugin.

- Add :IoEval: eval the given lines and put the output in a new window.
- Add <leader>io mapping to trigger the :IoEval command.
Merge branch 'ftplugin'