Move sources to `src` directory, update cabal

This should keep things a bit more organized as the number of Haskell
modules increases.
Migrage common argument parsing parts from Main

Since we're going to have two versions of Main (one for GNU-style
arguments and one for COP5555), this commit moves components that can be
shared between the two out of the main module.
Add hs-rpal-compat alternate argument parser

This command-line argument parser is compatible with the COP5555
reference parser.
Fix comment handling in lexer

Comments have to be handled before operators. Otherwise, they get
consumed by the operator handling. This reorders the lexer rules to
solve this.

The program now passes all the test cases.
Prepare for COP5555 Project 1 submission

- Add a `BUGS` file (that says that there are no known bugs)
- Make the Makefile match the given example Makefile
- Update version number to 0.1.0 (0.0.2 feels too small)
- Make both build targets static (why not?)