Adding support for syntax-quote, unquote, and unquote-splice

Changes:
- Added syntax-quote support: the reader macros `, ~, and ~@ can now be used
- Added support for a reader-expansion stage between parsing and evaluation
- Reader-macro support added for REPL, loading stdlib, and running code from file
- The way normal quote (') is expanded has been changed for compatibility with syntax-quote
- Moved reader-related code into a separate group
- Reader now supports special handling for `, ~, and ~@ tokens
- Fixed a bug where symbols were being improperly dereferenced when expanding a macro
- Added standard library functions/macros 'defn', 'not', 'and', 'or'
- Relicensed project under the EPLv1.0 (to allow use of Clojure stdlib code)