[~] fix plugin pj

https://github.com/robbyrussell/oh-my-zsh/commit/bce74975d055529cbd186782e2fd99e6da840460
Switch back to oh-my-zsh.hide-dirty setting again

Commit 81004dfaba509ff62a13ba303ab941938d619326 reverted the change
in 9b811fb625c03c30a766191cdf65a1c7c1fd96b2 when editing the merge
conflict from #2928.

This commit fixes that so that we don't make the same mistake again.

First seen in http://git.io/Cdaj5Q
Merge pull request #3323 from alfss/fix-pj

[~] fix plugin pj
Merge pull request #3333 from mcornella/fix-git-hide-dirty

Switch back to oh-my-zsh.hide-dirty setting again
Respect original PATH definitions on install

The exporting of PATH as a fixed string would clobber any system-wide
paths added to env after installation. Instead, we now read any existing
PATH exports from previous config files and copy those from the user's
bash config, or else default to a basic prepend-only example that
respects the system environment.
Use sed instead

This needs the extra newline character defined in a variable because
shells treat the ${} expansion differently for replacing newline characters.