TODO

@Next
* super(...)
* IO
* File
* Dir
* Kernel#require
* Fix {...} for blocks
* namespace constants in Module (A::B)
* break
* next

@Later
* Fix CallSite leak (see TODO in TrVM_lookup)
* begin...rescue...ensure
* def...rescue...ensure
* Proc
* String interpolation
* FFI
* Replace GC w/ smaller, simple & embeddable one (tricolor or refcount)
* Embed bytecode of /lib stuff inside executable
* ||= &&= +=, etc.
* Cache constant lookup
* case...when
* Float, Bignum
* Reimplement Array, Hash using Tuple like Rubinius or fix Hash to use #hash
* puts nil # => nil in MRI
* Implement & operator
* Run RubySpecs
* Fix operator precedence
* See TODO in code too!

@Someday
* Compile to file
* Sandbox
* Rubygem support w/ http://github.com/fabien/minigems
* REPL
* Unicode
* lightweight threads, coroutines (using libconcurrency?)
* JIT
* SIMD acceleration