conversion routines

[incanus]

• pixels <-> projected meters <-> coordinates
• meters/pixel at a given zoom & latitude

Precursors to point plotting #60 and interactivity #352.

Related: #97

Happening in conversions.

[incanus]

Just about set with this, including Cocoa bindings. Couple more things remaining; will try to hit in & around NACIS this week.

• get current tests passing
• write tests for new stuff (e.g. rotate map & test expected corner lat/lon, screen -> lat/lon -> screen equality)
• header docs for Cocoa

[incanus]

Header docs in cutting-room-floor/mapbox-gl-cocoa@2258147.

[incanus]

Tests are currently blocked by a weird instance of glsl-optimizer trying to be built against the iOS SDK:

/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS8.0.sdk/usr/include/sys/cdefs.h:680:2: error: Unsupported architecture
#error Unsupported architecture

https://travis-ci.org/mapbox/mapbox-gl-cocoa/builds/38308269

/cc @jfirebaugh @springmeyer

[kkaefer]

Removed glsl-optimizer in 080c185

[incanus]

Picked this back up again and working on merging master in, tweaking as necessary, and getting a squashed PR going as a precursor to user location marker (#756) and general client-side data such as markers (#507).

[incanus]

iOS-relevant stuff to bring over: https://github.com/mapbox/mapbox-gl-cocoa/compare/conversions Once I stabilize this, I'll ticket Android / other APIs we want (though those two are probably it).

[incanus]

Happening over in #853 now.