Fixed some #pragma mark statements in the Quartz Composer plugin.
Use the CGPathCreateWithRoundedRect() function when available to improve drawing performance.
Fixed building for iOS6.x.

This would build for iOS7 but not for iOS6.
Fixed a bug in the automatic labeling method that could cause an application hang with very small axis ranges. Fixed issue #52.
Changed some view coordinate calculations to use NSDecimal throughout to reduce rounding errors that occurred with very small plot ranges.
Merge branch 'fixes-to-push' of https://github.com/bignerdranch/core-plot into bignerdranch-fixes-to-push
Added back the run-time check when using the iOS 7 SDK since the app could be running on an earlier system version that doesn't have the new method.
Merge branch 'master' into release-2.0