Closes #203.

Use non-lazy enumeration for removal of dictionary keys.

In the current situation, iterating over `self.data.keys()` is OK only when
the dictionary is not modified, as `self.data.keys()` is lazily generated,
at least in Python 3.

Unfortunately, as we intend to change the dictionary with the `--purge`
option, we get a runtime exception when iterating the loop.

This commit fixes it by making the generation of the list of keys occur only
once, so that the dictionary itself can be modified in the body of the loop.

Tested with both Python 2.7 and Python 3.3.

Signed-off-by: Rogério Brito <rbrito@ime.usp.br>

fixed typo

The previous code was most probably a typo if i think.

Updated cygwin code

Disable export of PROMPT_COMMAND for bash shells.

Not using export means sub shells can't see the env
variable changes, but this shouldn't be an issue since
new sub shells should be sourcing ~/.bashrc anyway.

exporting the prompt seems to be too harsh and breaks the shell in Emacs as the PROMPT_COMMAND for xterm (say) overwrites the 'dumb' PROMPT_COMMAND, which now is 'contaminated' with ASCII escape strings.

normalize path ending before adding to the DB

Closes #188.

added a new option, -d/--decrease to decrease the weight of a path.
added --increase as an alias to --add for symetry.

Do not exit with error if current directory is the only match.

Closes #182.

Handle autojump errors when opening file manager.

Closes #177.

This reverts commit 49a0d702ba.

Conflicts:
	bin/autojump

Closes #178, #181.

Fix issue #179

Closes #178.

Revised README.md

Use named args when calling find_matches

This should make it clearer at first glance where True and False is
referring to.

`path` is decoded already (coming from `db`) and this caused the
following error:

    Traceback (most recent call last):
      File "/home/user/.autojump/bin/autojump", line 460, in <module>
        if not shell_utility(): sys.exit(1)
      File "/home/user/.autojump/bin/autojump", line 429, in shell_utility
        results = find_matches(db, patterns, max_matches, False)
      File "/home/user/.autojump/bin/autojump", line 374, in find_matches
        if current_dir == decode(os.path.realpath(path)) :
      File "/home/user/.autojump/bin/autojump", line 277, in decode
        return text.decode(encoding, errors)
      File "/usr/lib/python2.7/encodings/utf_8.py", line 16, in decode
        return codecs.utf_8_decode(input, errors, True)
    UnicodeEncodeError: 'ascii' codec can't encode character u'\xb4' in
    position 52: ordinal not in range(128)