Add the ability to disable casting of RDF::Resource
Protect Term#rdf_subject

Terms having public rdf_subjects created a pitfall users accidentally
trying to work with Terms instead of their member values. This tightens
up the API to prevent confusion.
Merge pull request #57 from terrellt/feature/CastingOption

Add the ability to disable casting of RDF::Resource
Removing code that was not called

Tests pass without this line. It does not appear to be necessary.
Merge branch 'removing-unneeded-code'
Adding array setters for terms

Previously setting a value by array index would fail silently. Now you
can set properties with []= (e.g. ```subject.title[1] = 'A title'```).
Accept terms passed into #set_value

Passing a term into Resource#set_value previously resulted in
unexpected behavior. This fixes that to set the current property to the
term's values, as though from an array.

Conflicts:
	spec/active_triples/resource_spec.rb
Refactoring tests for array setters
Merge pull request #46 from no-reply/feature/term_array_setters

Adding array setters for terms
Merge pull request #62 from no-reply/feature/protect-term-subject

Protect Term#rdf_subject
Merge branch 'master' into generate_id to include latest pushes to master
Add IDMinter class taking lambda function

Per recommendations from Tom Johnson, the following changes were made to this branch...
* remove generate_id method from Resource class
* add new IDMinter class with generate_id method
* change generate_id to take a lambda function for the minter; include UUID generator as the default minter
* update Resource.id_persisted? and uri_persisted? to call method in Repositories class
* add method has_subject? to Repository class which uses RDF::Repository.has_subject? to check for the existence of an rdf_subject in registered repositories.
** can specifiy a single repository to check.
** will check all registered repositories by default.
NOTE: Merged with latest master before updating branch in github.