Start building a driver around con.

Con can now run a few different ways:

    # launch the REPL
    $ con.rb # or con.rb --repl

    # execute (foo)
    $ echo '(foo)' | con.rb

    # execute the contents of foo
    $ con.rb -f foo

    # dump the token stream of (foo)
    $ con.rb --tokenize
    (foo)^D

    # tokenize the contents of foo
    $ con.rb --tokenize -f foo

    # dump the ast of (foo)
    $ con.rb --dumpast
    (foo)^D

    # parse the contents of foo and dump the AST
    $ con.rb --dumpast -f foo