Add help tooltip and refactor ajax loading indicators

 * Add Bootstrap Tooltip to profile tags header
  * Tooltip contains #hashtag help text
  * Style tooltip text
  * Increase tooltip font size
 * Move application.js to a coffeescript file
 * Refactor AJAX fetching indicator to be less obtrusive
 * Refactor showing gist fetching message to be less obtrusive
 * In OmniauthCallbacksController#github, set flash to indicate redirect was from OmniAuth callback
 * Add ApplicationHelper#render_fetching_info? to inspect flash and look for from omniauth callback key
 * Rewrite fetching messages to be more descriptive
 * Update robots.txt to allow bots to see homepage, but disallow authentication paths
 * Update humans.txt with My Gists info
 * On README, add thank you message to early adopters and link to contributors