Implement and test a well-defined semantics for repeated symbols in (let/(de)fnk) bindings:
- Optional values can reference symbols bound earlier within the same binding
- :as and :& symbols are bound before other symbols within the binding
- Across separate bindings, symbols can be repeated -- latest wins
Merge pull request #1 from Prismatic/defined-semantics-for-repeated-symbols

Implement and test a well-defined semantics for repeated symbols in (let...
Ensure guess-expr-output-schema doesn't capture non-literal keys
Ensure we compile with full speed under leiningen.