Instead of stating every directory to check if its realpath is the
current directory, only do so for any potential matches.

This regression bug was introduced when adding the KEEP_SYMLINKS option. The
current_dir was always set to '.' which would never match any database entries.

Closes #156.

Updated IPython autojump module to support new versions of IPython (0.11+)

Using --dry-run alone wouldn't default to --auto and therefore show different
paths that what would actually be used upon installation.

custom installations.

A few KB of disk space is not worth the logic overhead.

Done for consistency with other Linux programs (e.g. rsync, rename).

The install script didn't support the use of a destination directory, which can
be pretty useful e.g. to create packages.

Instead of keeping the version number in two separate places, the Makefile will
now grep bin/autojump for the proper version number.

Even though the previous version works fine on OS X 10.6.8, it seems to be
causing problems for other Mac users on 10.8.x. Unfortunately I do not have
access to a newer Mac to test on.

Update README.md with correct PROMPT_COMMAND.

The recommendation doesn't work with bash 4.1.5, the code in autojump.bash is fine, so use it here.

Minor formatting update for README.md

The previous test condition would cause errors because even though brew didn't
exist, the directory /share/zsh/site-functions did and it would throw error
messages on non-homebrew systems.

Make autojump work with Python 2.6 again: vendorize argparse.

This adds the argparse library [1] as autojump_argparse and imports it
via sys.path mangling in case argparse does not exist (Python 2.6 or
below without argparse installed).

This makes autojump effectively work with Python 2.6 again by default.

I have not verified license compatibility, but given the intention of
the (backport) project this is likely OK (it is licensed under the
Python license).

1: http://code.google.com/p/argparse/

Fixes issue #121.

I've updated the documentation to notify end users to add compinit to their
~/.zshrc if they want tab completion.