Look for `ack-grep` executable before using `ack`.

`ack-grep` is the default name on Debian/Ubuntu at least.
Merge branch 'master', remote-tracking branch 'origin/master'
Escape `|` in args to ack.

This fixes https://github.com/mileszs/ack.vim/issues/#issue/14 ("Search
with "|" blows up").
Merge remote-tracking branch 'origin/master'
Remove .README.md.un~
make Ack suport longer argument list.
README: add Fedora install instructions
AckHelp and LAckHelp commands added
AckHelp related fix
AckHelp unneeded quotes removed
Merge pull request #44 from ciupicri/patch-1

README: add Fedora install instructions
Merge pull request #16 from blueyed/master

ack.vim improvements
Update README.md
Forgot a closing parenthese.
Enabling auto detection of Ubuntu Debian in place of comment

It took me a while to track down why Ack wasn't working for me, so in order
to save others the trouble of tracking down the comment in ack.vim I've
added detection so that it will just work for Debian/Ubuntu users as it
does for others.
Simplifying the install instructions to reflect Debian auto detection
Quick fix of a peroid that I accidently removed from the README
Refactoring after seeing "github.com/blueyed"'s awesome work
Merge pull request #24 from gnap/master

make Ack suport longer argument list.
README: Add installation instructions for FreeBSD.