Consolidated pull requests preparing for 0.1.1

With this branch I'm trying to merge the various open pull requests to support an official 0.1.1  release in the not too distant future.

**What I've done to this branch so far:**
1. Merged my commits from #20 (MBTiles) which fix issues https://github.com/mapbox/mbxmapkit/issues/3 and https://github.com/mapbox/mbxmapkit/issues/7
2. Merged my branch for https://github.com/mapbox/mbxmapkit/pull/21 (Maki markers & simplestyle) which fixes issues https://github.com/mapbox/mbxmapkit/issues/5 and https://github.com/mapbox/mbxmapkit/issues/9. This had some conflicts with the MBTiles code, so I resolved that stuff.
3. Merged my branch for https://github.com/mapbox/mbxmapkit/pull/23 (cache stuff) which fixes issue https://github.com/mapbox/mbxmapkit/issues/22
4. Merged @jparise's branch for https://github.com/mapbox/mbxmapkit/pull/27 (image quality api)

**My present todo list:**
1. Figure out what's going on with the podspec (see https://github.com/mapbox/mbxmapkit/issues/34) and get it working, ideally including the correct stuff for libsqlite3 so that the ifdef's can be removed from the MBTiles code
2. Finish my branch for overzooming. So far I've got it working for MBTiles on iOS, as I described at  https://github.com/mapbox/mbxmapkit/pull/20#issuecomment-34540499, but I also need to get it working for online tiles (see https://github.com/mapbox/mbxmapkit/issues/35).
3. Re-work the existing sample apps, or perhaps add more build targets, for the purpose of demonstrating how to use the various new features.
4. Test all this stuff to make sure it compiles and works properly on both iOS and MacOS. In particular, there's a real good chance that the image manipulation code for overzooming will need changes to compile on OS X.
5. Update the documentation and maybe write a tutorial or two.