Add detection for IE Compatibility View

This adds the method ie_compat_mode to use to determine if the browser is IE in the compatibility view mode.

This also removes an invalid IE UA string from the tests and fixes another UA string that was also invalid, both from commit 3c727f5.

Fixes #74

The detection added here is exactly how IE 8-11's compatibility mode works: they always send `MSIE 7.0` but include their real Trident token. The Trident version actually needs to be checked for `>= 4` (which is IE 8, the version compatibility mode was added), though, because the original Windows Phone OS actually comes with IE7, but since it came out after the IE team wanted to add the Trident token, they added one of 3.1.