ssh-select-key, resource and link functions added.

.bash_functions:
- ssh-select-key for selecting default ssh key (link key to
  id_rsa{,.pub};
- resource for sourcing ~/.bashrc;
- link for creating symlinks;
- die now calls "return 1" instead of "exit 1", for usage in bash
  functions;
- warn function for warning messages (yellow);
- Minor formatation tweaks.
Detecting and removing trailing whitespace in vim.

.vim/vimrc:
- Added highliting for trailing whitespaces;
- Function StripTrailingWhitespaces() added;
- Added autocmd for executing StripTrailingWhitespaces()
  automatically on save.
Merge branch 'master' of github.com:mtpereira/dotfiles