Find appropriate selector without NSString allocation
Rewrite using sel_registerName()
Makes argument count to SEL calculation only once

To avoid unnecessary calculation on each invocation,
I hold the argument count to SEL conversion table statically.
switch-case jump only small arg count
Add case of arg count = 0
RIP NSObject.rac_lift
Revert "Add case of arg count = 0"

This reverts commit c0f44328d9863ce869ddd3a5adf1df173e52d1cb.
Revert "switch-case jump only small arg count"

This reverts commit b0fe38a81ff9642bc288bee7c3c8d44cd625b9b7.
Revert "Makes argument count to SEL calculation only once"

This reverts commit 3a2bf1d6903d1e7031fd1c35e243efae80d0a7f8.
Revert "Rewrite using sel_registerName()"

This reverts commit df992ea436b81dc2e1e017a39c81f9d658b831a8.
Refactor all lifting methods to only accept signals

Also added a nil terminator requirement to
-rac_liftSelector:withSignals:, for consistency with block lifting and
other variadic methods.
Delete dynamic selector generation code
Add case 0 for clarity
Re-add old methods as deprecated/unavailable
Minor stylistic tweaks
Merge branch 'zero-alloc-selector-search' into 2.0-development (pull request #602)
Remove libextobjc submodule
Read part of libextobjc into the ReactiveCocoa folder as a subtree
Re-add jspahrsummers/xcconfigs into the external/ folder
Fix up libextobjc and xcconfig project file references