Add JSX filetype detection

Taken from @wincent:

  https://github.com/wincent/wincent/blob/master/.vim/ftdetect/jsx.vim
Add some words to custom dictionary

- immersive
- stylesheet
- codebase
- dropdown
Change joe.lencioni@causes.com to joe.lencioni@brigade.com

New company, new domain name, new email address.
Add snippet for creating React components

This is my new component file template which contains all of the things
that I need to do every time I create a new React component.