Fix incorrect use of partial

Fixes #1002
Fix indentation error reported by syntastic
Merge pull request #1005 from ZyX-I/fix-1002

Fix incorrect use of partial
Make shell client work in OS X:

- use gnu env for `env -0`,
- use filesystem socket.
Update shell powerline client OSX requirements in documentation
Merge branch 'osx-shell-client' into develop
Explicitly print exception from :try block

Reason: :try takes any output to the stderr as the exception, so traceback is 
never printed even though nothing is caught.
Balance error message text
Do not emit a warning about symlinks when it is not the problem
Do not remove one component from directory path
Normalize all paths before doing anything else
Move one if check into python code

Reason: this removes one useless indentation level that breaks “tabs for
indentation, spaces for alignment” rule.
Merge pull request #1025 from ZyX-I/fix-vim-troubleshooting

Fix some issues in Vim troubleshooting code