Alternate strategy to detect unlink failure

Closes #12.
Don't prompt to read after automatic chmod
Provide :SudoEdit
Fix formatting issue
Spelling fix
chmod doesn't accept -- on OS X

Closes #16.
Automatic mkdir in :Move and :Rename

Closes #11.
Provide :Mkdir

Closes #13.
More robust 'noreadonly' for :SudoEdit
Better filetype detection with sudoedit

BufEnter is absolutely the wrong event to use here, but using
BufReadPost won't override an incorrectly detected "conf" type.
Support old Vim without fnameescape
Document non-commands
Further tweak of :SudoEdit 'readonly' override
Use sudo -e to drive reading/writing

This means permissions for sudoedit will be used rather than cat/tee,
which could mean fewer password prompts.
Complete directories for :Mkdir
Rename :W to :Wall

References #9.
Easter egg
eunuch.vim 1.1

* Provide :Mkdir.
* Automatic mkdir in :Move and :Rename.
* Make :Rename relative to containing directory.
* Fix :Chmod error.
* Rename :W to :Wall.
* Skip unwritable buffers in :Wall.
* Provide :SudoEdit.
* Show password prompt for sudo in GUI.
* Better filetype detection for files edited with with sudoedit.
* Support old Vim without fnameescape.
Fix syntax highlighting after chmod +x

Closes #17.
Restore grepprg in correct window