Update existing resource without envelope id

[coffeejunk]

Allow users to update an existing resource without knowledge of it's envelope_id using a POST request.

Fixes #99

[coveralls]

Coverage increased (+0.003%) to 99.593% when pulling c6beee9 on coffeejunk:update_without_id into a215670 on CredentialEngine:master.

[coveralls]

Coverage increased (+0.003%) to 99.593% when pulling c6beee9 on coffeejunk:update_without_id into a215670 on CredentialEngine:master.

[leolara]

@coffeejunk

I do not think we should based this specifically on cterms:ctid field and ce_engine community:

• Not all entities have cterms:ctid in the ce_engine community
• All entities in all communities should have @id field

Hence, I think it should be based on the @id field. Also, we should consider the community prefix for @id

[leolara]

@coffeejunk what about my comments?

[coffeejunk]

@leolara I've changed the retrieval to use the @id instead and check if a prefix is used.

[coveralls]

Coverage increased (+0.003%) to 99.593% when pulling fd0e0a9 on coffeejunk:update_without_id into 2e58617 on CredentialEngine:master.

[coveralls]

Coverage increased (+0.003%) to 99.593% when pulling fd0e0a9 on coffeejunk:update_without_id into 2e58617 on CredentialEngine:master.