[Bash] Large changes to Bash

    bash_aliases:
        * Remove unused alias, diff=vimdiff
        * Remove alias to color grep output. Set ENV variable for that in
        bashrc

    bashrc:
        * Export GREP_OPTIONS variable to colour output of grep
        * Split functions into bash_functions file
        * Ignore *.o files for completion too
        * Prevent bash from attempting to do path completion on empty lines
        * If files in $FIGNORE are the ONLY possible completions, show them
        * Enable ! style history substitution
        * Ignore the case when giving completion hints
        * When attempting to complete from within a word, skip the amount
        that is already typed
        * Show a list of detached screens atleast once

    bash_functions:
        * Moved all functions from bashrc to here.
        * Add some amount of documentation for each function
        * Add new function, calc(), a simple calculator for the command line
        * Add new function, tre(), a shorthand for tree with a bunch of
        preset settings
        * Add new function, cat(), which uses pygmentize to display coloured
        output
[ViM] Update spell file