Added option to use external nose python modules
Add a virtualenv for testing external nose
Add tests for externalNose
Move activation_tools and include on path if necessary
Add default value of externalNose to docs
Add a placeholder in the lib dir

Makes sure that the directory exists when the devsetup script is run, and
prevents us from having to do nasty hacks due to mkdir not accepting
forward slashes on windows.
Merge pull request #6 from thusoy/pr/5

Add externalNose option

Closes #4 and #5.