Removed vimshell.

Removed vimshell because it's just not very robust. In general,
gnome-terminal with bash is quite a bit faster in terms of performance.
Speed in terms of typing commands can be reconciled somewhat by
copying/pasting from vim or modifying the clipboard option. In general,
my strategy will be to use <leader>gt to pop terminals when I need them
and then close them when I'm finsished with them.
Made commands which jump to locations in g:vimfiles portable