bash: prompts displays the current virtualenv
xsession: center the wallpaper
Vim: don't open the first result of Ack-ing
Add ctags
Vim: add tags mappings
bash: fix profile and rc configs

My previous configuration caused trouble when running inside tmux. I got
an error that __prompt_command is undefined. This is due to the fact
that PROMPT_COMMAND got exported and is inherited by the child bash
process but it doesn't contain the necessary definition because tmux
starts it as a login shell.

Currently I load .bashrc for all interactive shells (both login and
non-login) so the above is no longer a problem.