Improve gf handling in Chef recipes

change Chef ft to ruby.chef instead of chef.ruby. This allows Chef
settings to override Ruby settings where necessary.

Move path settings from .vimrc to Chef FT plugin.

Append local directory (.) to path for Chef files. This will make 'gf'
work for recipes in the same cookbook recipes dir.
Fix includeexpr, path, isfname to improve 'gf' for include_recipes
Make gf work with include_recipe 'cookbook::recipe'

Set isfname+=:
Create Chef ftdetect and ftplugin

Initially, make 'gf' work on include_recipe
Merge branch 'chef-ft'

Conflicts:
	ftdetect/chef.vim