`:Hg!` command changes: - Ability to edit in a normal buffer instead of the preview window. - Set syntax coloring according to the Mercurial command. - Updated the documentation. Miscellaneous cleanup. New pretty banner in the documentation. New "global settings" section in the documentation. Added `graphlog` syntax file.

" LAWRENCIUM - MERCURIAL COMMANDS FILE TYPES
"
if !exists('g:lawrencium_hg_commands_file_types')
    g:lawrencium_hg_commands_file_types = {}
endif

let g:lawrencium_hg_commands_file_types.diff = 'diff'
let g:lawrencium_hg_commands_file_types.glog = 'hggraphlog'