Update Mapbox.podspec

GRMustache was not updated, but the submodule was.
Merge pull request #408 from GannettDigital/release

fix GRMustache pinning in podspec
update docs in podspec
add new docs scripts
Merge branch 'release' of github.com:mapbox/mapbox-ios-sdk into release
fixes #443: merge heading fixes from @htthach
clarify pull request policy
clarify pull request policy
new resource bundle format
Merge branch 'develop' of github.com:mapbox/mapbox-ios-sdk into develop
namespacing tweak
new resource bundle format
namespacing tweak
merge develop for 1.2.0 release
update changelog for 1.2.0
bump podspec for 1.2.0
correct changelog for background count
added great circle docs
merge release back into develop
clean up constraints