Make sure processing of stack items converts them all from `Variable` and `Function` instances to the right thing for special commands. Added more tests. Improved README.
1.0.21
Improved error handling / reporting. Added `--print` option to auto-print results of operations.
1.0.20
Use new `findStringAndArgs` and `findCallableAndArgs` utility functions to find strings (for `join`) and callables (for `map`, `apply`, etc) plus their arguments on the stack
1.0.19
Added `join` special function and `:r` (reverse args) modifier, plus tests. Updated README.