Experiment with many changes.

- Add the vim-airline plugin for a new status line.
- Organize the vimrc with nice section headings.
- Add various new mappings and preferences, mostly adapted from
  https://github.com/amix/vimrc
Use git hooks to auto-generate ctags.

- Use git hooks to auto-generate ctags per
  http://tbaggery.com/2011/08/08/effortless-ctags-with-git.html
Add more experimental vimrc changes.
Merge branch 'experimental' of github.com:jordal/myrc into experimental
Change the highlight color for long lines.
Merge branch 'master' into experimental
Set the scrolloff setting.
Merge branch 'experimental' of github.com:jordal/myrc into experimental
Merge branch 'experimental'
Update taskwarrior color scheme file path.