Adding repetition parsing / validation

[minjit]

see title

fixes #6

[azoner]

Nice work. I want to think a bit about the interface changes necessary for repeated values.

For backward compatibility, get_value() should return the element value for no repetitions and the formatted element list including the separator for repeats.

I'd like a get_values() method that returns a tuple(string). Elements with no repetitions would just have a single element tuple.

[minjit]

Sure, I can take a look at that.

[minjit]

Get_value was already backwards compatible. Added the get_values_list method. Named it that way for clarity and it returns a list instead of a tuple because we're building a list anyway, but can convert it to a tuple at the end if you'd prefer.

[coveralls]

Coverage increased (+0.5%) to 67.526% when pulling 3ed4711 on minjit:master into 2289ea8 on azoner:master.