Remove watching of vendor files

When appending repositories from GIT the number of files in vendor quickly adds up, which leads to a really fuzzy too many open files error in nodejs, also described in http://stackoverflow.com/questions/8965606/node-and-error-emfile-too-many-open-files

Restarting your `grunt server` after adding vendor scripts seems more reasonable than the EMFILE error, which cost me one hour googling+debugging.