making `lam` be a keyword and recognize it as an alias for `fun`, in preparation for changing the syntax of lambda expressions.
Merge branch 'new-world' of github.com:brownplt/pyret-lang into new-world

Conflicts:
	src/arr/compiler/desugar-check.arr
fixing broken tests after the merge
new bootstrap with arrays and lambda token support merged in
fixing printing of lists to the new constructor syntax, and adding a tostring method to arrays
renaming all anonymous funs to lams, in compiler and in tests
new bootstrap with only lam tokens for lambda
fixing remaining uses of list literals
new bootstrap with lists fully excised and replaced by array constructors
fixes for tests, and now everything passes