various improvements to configurations

- added a default .gitignore file for git
- added a default .ackrc configuration for ack
- made exit code in bash prompt bold red if it's non-zero
- various improvements and mappings for .vimrc
- refactored .bash/gitprompt.sh
- small changes to .screenrc, .inputrc, .bash/environment.sh and .bash/options.sh
- improvements to README file
- added screenshot with glimpses of screen, vim and bash prompt
- added .ackrc and .gitignore to copy-files.sh script