detect script directory to make bash and zsh usable without having `powerline` in `$PATH`
workaround for _powerline_tmux_setenv() issue with bash-4.2.45
Avoid infinite recursion in `POWERLINE_OLD_PROMPT_COMMAND`

Fixes #678
Make clearer the naming conflict in PyPI (closes #681)
Fix weather geoip lookups

- _external_ip() isn't necessary with freegeoip.net as it does this for you when unspecified.
- region_name/country_name make Yahoo's weather API unhappy whereas region_code/country_code work for me (TX/US)
Fix powerline-lint tests

Some notes on the commit:

1. As external_ip and email_imap_alert segments seem to be removed corresponding
   segment_data keys also were removed.
2. Various files that import vim module now have the usual workaround that sets
   vim local to dummy object on error.
3. Syntastic check was failing because it did not specify which highlighting
   groups it uses in documentation. I made it specify them and also moved format
   strings to keywords. Same for some other plugin-local themes.
4. powerline-lint script got --debug argument. Pretty useless currently though:
   it only makes it output traceback for ImportError when failing to import
   module to stderr.
5. Moved themes/vim/plugin/*.json to themes/vim/plugin_*.json.
6. Fixed powerline-lint that ignored problems from values.
Make sure flake8 does not show any errors in powerline/lint/**/*.py files
Set TMUX_PWD_* on startup

Ref #672
Do not mention zpython branch

It is not usable due to some bugs, not maintained and replaced by 
powerline-client
Add jobnum segment

Replaces #596. Differences:
- Tests and metavar.
- Uses “jobnum” name in place of “jobs”.
- Does not use subshell for zsh. Also counts jobs correctly in zsh.
- Adds an option to force showing jobnum segment even if there are no jobs.
Pass run_once to ConfigLoader, make it respect run_once

It only respects run_once by using DummyWatcher instead of a watcher doing 
something potentially useful

Ref #711
Test that nothing is reloaded with run_once=True
Make sure watcher is not used
add Solarized Light colour theme for Vim
Update solarizedlight.json

Update name to "Solarized Light".
Remove Gentoo ebuild and reference raiagent overlay
Merge pull request #722 from ZyX-I/raiagent-overlay

Remove Gentoo ebuild and reference raiagent overlay
Merge pull request #695 from ZyX-I/powerline-lint-fix

Fix powerline-lint tests
Merge pull request #712 from ZyX-I/shell-jobs

Add jobnum segment
Merge pull request #697 from ZyX-I/zsh-bindings-small-update-1

A few fixes to zsh bindings