Various critical fixes

-concat bug fix, documentation improvements

Added -throttle:valuesPassingTest:, Xcode fixes

Add the current directory to USER_HEADER_SEARCH_PATHS

Warning updates

Add Test configuration for unit test targets

Fix header paths for uninstalled iOS products

Fix disposed subscriptions getting events, improve dealloc disposal

Fix -concat dropping signals and not always disposing

Optimizations

Fix rac_command concurrency, only run -rac_description in DEBUG

Added +once: and -ignore:, minor code and documentation cleanup

Fix RACDynamicSequence leaks

-collect converts nil -> NSNull, -toArray returns nil on error

NSRange support for rac_returnValue

Stream naming optimizations, fix stack clobber in RACArraySequence

Type encoding fixes, +schedulerWithQueue:name:, -rac_gestureSignal

Memory management fixes, fix RACAbleWithStart behavior, optimization

-rac_signalForSelector:, -objectPassingTest:, miscellaneous fixes

Add -all:, fix commands never completing, add -rac_didDeallocSignal