Merge pull request #146 from Prismatic/deprecate-old-syntax

Deprecate old ^{:s } syntax
Deprecate the *use-potemkin* flag and provide a new experimental way to configure this
Move public macros from schema.macros to schema.core:
 - Move canonical implementations to schema.core
 - Leave deprecated stubs in schema.macros (with actual implementations, for now)
 - Remove dependence on potemkin/import-vars, which was causing problems with AOT
 - All tests pass at this point, referring to old schema.macros locations
Move all tests and docs to point to macros in schema.core/, not schema.macros:
 - Stop using old deprecated versions of macros
 - Switch to using :include-macros true on schema.core in ClojureScript
 - Bump min cljs version to 0.0-2120 for :include-macros support