Factor out PointerIdentity.
Rebase ishakawa/print-module-to-fd onto master. Closes #8.
Add implementations of Target, TargetMachine and TargetDataLayout.
YARD error fixes.
Properly initialize native/all targets.
Deprecate LLVM.init_x86 in favor of new LLVM::Target API.
Update PassManagers to be compatible with both ExecutionEngine and TargetMachine.
Merge remote-tracking branch 'whitequark/ptrid'
Merge whitequark/target (and make ARM test conditional.)
Fix llvm-config path in generate_ffi for portability.
Freshen README
Update intro
Added 'see also' section
Overhauled gemspec

* Added version constraints for key libraries
* White list ext/ files (don't include .dylib and .so files)
* Updated description