Implemented set-bang
Implemented syntax-expansion for letrec
Implemented named-let via syntax expansion
it is accepted by the server now

Basically had to add one prim-proc so that monster of a method is even
bigger now.
Fixed error messages for set-bang
Merge branch 'letrec-syntax-expand' of https://github.com/taylorj7/Interpreter into letrec-syntax-expand
Added reset-global-env
added void and expanded while

basically just had to add void as a prim-proc in order to implement
while as a named let.
Ribcage-environments completed. That was actually really easy
Added a vector-add-left command. Returns a vector that is the old vector with a new item added on to the front
Eh, changed vector-add-left to vector-add. Adds to the end. Makes no big difference, but more consistent with how memory should probably work.
Merged changes in interpreter.ss. Also fixed use of if-exp where if-true-exp would be more appropriate.
Changed all implicit-lambda defines to non-implicit variants, in preparation for defining define in the interpreter, and the possibility of a self-interpreting interpreter.
Added define-exp as a datatype. Also changed back to vecto-add-left because cons is easier than snoc.
Added parse-exp and unparse-exp cases for define-exp's. Also removed unnecessary check of pair? in parse-exp.
tiny commit

interpreter
define works now.
Implemented load. We should probably do call-by-ref first though.
Gotta close that input file when you're done with it, Jimbo
Accidentally a parenthesis