restructure parser's `program`

Limits return statements to the function block. Allows statements at
base level
allow base level statements

closes #52
fix compiler executable build
Merge branch 'sast' into scripts
small fix
Merge pull request #55 from rapid-lang/scripts

Scripts
println should print anything
include all info in var decl AST node
Merge pull request #56 from rapid-lang/var_decl_refactor

Var decl refactor

Everything looks good to me