Don't show '//' when using path separator

Currently, the cwd segment is showing //etc when we are in /etc and / when we are in the root file.
This small patch fix this
Fix display for home directory
New fixed segment showing position of current view

Solves #539
Fixed version of #540 and #579
Works now for split windows and wrapped lines.
Add powerline/bindings/fish/powerline.fish
Make fish bindings feature complete, add documentation

Added features:
- Updating TMUX_PWD_* when PWD variable changes
- Updating TMUX_COLUMNS_* when WINCH signal is received
Add support for number of jobs to fish bindings
Merge branch 'develop' into feature/539-position-segment
Small fixes for new position segment

- use vim_funcs
- use a dictionary instead of a tuple for translation strings
Add fish tests
Fix Syntastic deprecation warning

`hasErrorsOrWarningsToDisplay` has been deprecated in Syntastic.
See: https://github.com/scrooloose/syntastic/commit/d629be9

This fixes the warning that appears when opening a new file:
"syntastic: warning: function hasErrorsOrWarningsToDisplay() is
deprecated, please use !isEmpty() instead"
Merge pull request #759 from fitztrev/syntastic-errors

Fix Syntastic deprecation warning
Improve test_shells/test.sh:

- Add argument that makes it run only one shell
- Make this argument also force skipping removal of tests/shell directory
- Make it copy logs to tests/shell before and after processing
Make postproc.py only leave fish prompt

Should fix fish tests
Another attempt to fix fish on travis
More test cases for position segment
Merge pull request #750 from EinfachToll/feature/539-position-segment

New (fixed) segment showing position of current view
Also output full.log

Hope it will give some hints about why fish tests fail on travis
Make XDG_CONFIG_HOME point to writeable location
Use `.` for sourcing in fish

It appears that travis uses fish version without this command. Though `.` is 
deprecated on new versions it is still supported for backwards compatibility, 
thus may be used here.
Also print shell version string