use custom .jshintrc options if they exist

If a custom .jshintrc exists use options defined there
instead of default options.

Look in the following places and if .jshintrc exists
return those options.

env.TM_DIRECTORY
- the directory of the current textmate file

env.TM_PROJECT_DIRECTORY
- the directory of the current text mate project

env.HOME
- users home dir

Otherwise return default options.