Add help tooltip and refactor ajax loading indicators

[simeonwillbanks]

• 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