Expose parseInput via Cite

[larsgw]

Expose the currently private parseInput method on Cite, and change the way Wikidata ID strings are parsed. This should make writing test cases (#22) and async parsing (#29) easier.

[larsgw]

The new structure will expose the chainlink way of parsing better, for mainly testing. Currently, the structure is this:

1: parseInput ---> 2: parseInputType ---> 3: parseInputData ---> 4a: repeat from step 1
                                                             \-> 4b: return data

A better way would be to have a while loop in parseInput() that repeats parseInputType() parseInputData() until the wanted format is achieved. These can then all be individually tested and used.