Added events for loading ads
Moved community-specific styles to community
Make tabs component more configurable
Update the tabs component to look a tad more like our other components
Fix the code highlighting for markup on the proximity loader page
Add Tabs styleguide page
url_validator raises InvalidUrl error when nil is given

This fixes "cryptic" errors that we were getting from Airbrake. If
anything goes wrong with #heuristic_parse it's perfectly fine to raise
InvalidUrl error and handle it.

```
Addressable::URI.heuristic_parse(nil) #=> nil
nil.path #=> NoMethodError
```
Ensure Stumble Upon button triggers a new window
Update adsense template
Added spec for ads visible/hidden events
Merge pull request #817 from lonelyplanet/if-adsense

Update adsense template
Merge pull request #799 from lonelyplanet/bart/abuse-flag-fix

Added events for loading ads
Merge pull request #816 from lonelyplanet/chee/stumbleupon

Ensure Stumble Upon button triggers a new window
Merge pull request #809 from lonelyplanet/bart/community-pagination

Moved community-specific styles to community
Merge pull request #812 from lonelyplanet/remy-tabs_update

Update the tabs component slightly.
allow external results to point to the correct location
Merge pull request #815 from lonelyplanet/chee/bug/external-search-results

fix the this: https://trello.com/c/Bgun5Hhe/340-global-search-redirects-to-wrong-page-for-guides
Initial work towards page hopping
Get content rendering
Fix broken charts on non /performance pages