Add aliases to req.gettext to fix jsxgettext

jsxgettext doesn't recognize `req.gettext()` calls.
The callee must be named `gettext()` to work properly.
Rename localePath to localeDir, default to locale/

localePath is ambiguous when compared with pubKeyPath and privKeyPath.

Defaulting to calling the folder 'locale' just makes more sense to me.
Ignore the locale folder
Merge pull request #87 from mozilla/i18n

Make string extraction work