Accept a count with :Gstatus <C-N>/<C-P>
Allow <C-p> pass through to ctrlp.vim in :Gstatus

This only works on the first line.  Any more than that, and we'll have
to give up on the whole <C-p> map entirely (which is not off the table).
Support ctrlp.vim in historical buffers
Pick sane git_dir for :Gedit from :Gstatus window

When using a :Gedit command from the :Gstatus window the git_dir was
being based on the window that was switched into in order to edit the
file. So if Fugitive switched into a window with a file from a different
Git repo (or a file with no Git repo) the :Gedit command could fail or
edit the wrong file.

Instead base the git_dir on the window from which the :Gedit command
originated.
s:Detect: only add readable files to &tags and doc

Fixes issue #104.
Fix A in :Gblame with unix timestamp
Allow a count to blame resizers

Pass a count to A or C to add that many additional columns, or to D to
remove that many additional columns.
Don't show diff in keywordprg output in GUI

It's not very readable without syntax highlighting or pagination, so
leave it off.
Update :Gblame supported options
Conceal file names and line numbers in :Gblame
Fix :Gbrowse when argument starts with a digit
Mention OS X browser in FAQ

Closes #255.
Correct foldtext when diff.mnemonic is set
Provide failsafe for foldtext filename

Closes #216.
Replace :Gstatus cv with cva and cvc

My rebuttal to #263.
Escape # in :Glog

Closes #265.
Allow :Gbrowse on HTTP GitHub FI

Closes #272.
Fix error when g:fugitive_github_domains is unset

Closes #274.
Send :help :Gw to the right place
Return '' from buffer.path() if outside work tree

In reference to #278.