Renew Vim color settings and themes

Based on the 'xoria256' theme (now use 256 color mode as well),
a little highlight/color settings were overriden and reconfigured.

To provide base colorscheme, added a vim bundle 'vim-colorschemes'
which contains a bunch of colorschemes available.
Add 256-color compatibility for screen and shell
Add Vim bundle tagbar

Keymaps: <leader>t for toggling tagbar.
Merge branch 'vim-color'

Conflicts:
	.gitmodules