Proper Mutation Support

[comraq]

• differentiate between mutable and constant bindings
  • consider using GADTs
• refactor source code to better modularization

[comraq]

• also need to update vectors to using the new mutable LPointer construct

[comraq]

• vectors created from procedures are now wrapped behind LPointer
• need to evaluate parsed lists/vectors directly into pointers (IORefs)
  • however parser is not in IO (dont think it should be)