Update of endpoints, uuid creation, test fixing

[jonnybazookatone]

Addresses the issues #1 and #3.

• The endpoints were changed so that they refer to only the UUID of the library, e.g., /libraries/. This should be permanent unless a user deletes the library (or owner account without transferring ownership).
• Class included so that PostgreSQL does not need to be used if not wanted in the future. The class allows UUIDs that are of PostgreSQL type, otherwise it uses a string type.
• The header from ADSWS API will contain the api user ID.
• Tests were updated to no longer pass a user ID in the URL, and via the header instead, mimicking that of the ADSWS API.

[coveralls]

Changes Unknown when pulling 84501702823157312c400c15f13d9ee77c959917 on jonnybazookatone:master into \ on adsabs:master**.