Move several settings and mappings to vimrc.local

I think it makes sense to move more settings into the vimrc.local file
since it's still available but the basic file under version control
stays unobjectionable. I'm open to debate on these but here is my
reasonning for each:

- the foldmethod line causes random files to open up folded for me
- nowrap makes it so you can't see everything on the screen at once
- hidden causes problems if you try to open files in new vim instances
  without fully closing out of your original vim session
- it looks like mappings depend on the leader definition at the time the
  mapping is made so it seemed to make sense to move the mapleader line
 and all the mappings that might depend on it together into the local
 file
Fixing shebang on install script

/usr/env didn't work for me, does this work on other systems? Will my
suggestion of /usr/bin/env break it elsewhere?
Implementing feedback on vimrc.custom file

- change back to agreed mapping of <leader>f for NERDTreeFind
- remove confusing comments about alternate mapleaders
- remove my weird <leader><space> mapping from the vimrc.custom file
- didn't move the "hidden" option back to the main file because it
  proved contentious
Merge pull request #4 from boombador/master

Moving some settings to vimrc.custom