initial commit
Add scaffolding for testing interpreter.
ignore vim's .swp files.
handle literal numbers.
add builtin arithmetic
handle compound expressions.
cleanup: use 1 interpreter for most tests. eval of a compound should eval the arguments, not apply.
add separate s-expr parser
add conditional evaluation. Fix argument evaluation bug.
add environment class
move builtins to the global environment for the interpreter
implemented lambdas
add let to special forms.
make lambdas handle recursion correctly.
add readme