Increase ulimit and add node_modules to PATH.

Increase the maximum number of open file descriptors to 2048 to deal with gulp
issues: https://github.com/sindresorhus/gulp-imagemin/issues/10. Prepend
node_modules/.bin to PATH for easier use of project-specific node modules.
Set up virtualenvwrapper.
Disable fast-forward merges.
Remove trailing comma.
Ignore .DS_Store