Add mementoweb.org aggregator as a source

[machawk1]

Related to #327.

The JSON endpoint for TimeMaps is formatted slightly differently than MemGator instances, so will need to be adapted.

https://timetravel.mementoweb.org/timemap/json/

• [ ] Add aggregator entry into array
• [ ] Fix binary fall-through implementation (related #327)
• [ ] Adapt JSON parsing algorithm to adapt to mementoweb's style cf. MemGator's JSON endpoint