initial commit of custom help file
Minor cleanup of vimrc. No functional changes

Also, remove duplicate diffopt setting
Rename help dir to doc/
Merge branch 'master' into custom_help
Merge branch 'master' into custom_help
Rename help file to mirror_pond.txt
Merge branch 'master' into custom_help
First pass at documenting keymappings
Add Insert/Normal/Command mode headings
Merge branch 'master' into custom_help
Document Fugitive mappings
Document plugin and filetype plugin mappings
Merge branch 'master' into custom_help
Remove \cf mapping for Ctrl-P

Awkward mapping better served by just hitting <CTRL-p>
Add <unique> to netrw_ret map
Unmap legacy commentary \ maps

Less clutter is good
More work on mirror_pond help
Inital pass at help file

Fixes #3
Merge branch 'custom_help'