bashrc: Account for latest XFCE terminal.

The current version of XFCE4's terminal sets COLORTERM to xfce4-terminal
(previously it was Terminal).
vimrc: Minor changes.

- Automatically detect indentation for all existing fies.

- Do not automatically strip all trailing whitespace on save, since this
  is unfriendly to existing codebases with trailing whitespaces. Make F6
  strip trailing whitespace.

- Removed use of tags in preparation for a better solution.
vim: Updated surround plugin to 2.0.
vim: Added Syntastic.
vim: Added YouCompleteMe.