Add various .gitignore patterns.

This combines the changes to .gitignore from three commits:

91847d1a added oauth token to provide composer with github login credentials
75681907 added git config
d26d7b8c added dev config and some gitignore entries

via `git diff d26d7b8c^..91847d1a  -- .gitignore`, except

`vendor/*` is changed to `/vendor` so it does not match:

    themes/bootstrap3/js/vendor