Rename attributes

Fixes #1.

I've tested this change manually by removing the local copy of `PagerSlidingTabStrip.Net` from my Xamarin app, and instead linking to my fork with the changes below applied.

I'm using the newer `Xamarin.Android.Support.v4` library from NuGet rather than the old `Mono.Android.Support.v4` library included in the `Xamarin.Android` toolset, so I updated that too.

I haven't bumped the version number, nor have I changed anything in the `Example` project.