Extracted find functionality from the create method

[andru]

It was useful to me to have a simple way to find if a model matching a set of attributes exists without necessarily creating it.

This pull request extracts the logic responsible for finding a model in the model.all collection from the model.create method into a new model.find. The model.create method is updated to use the new find method.

• Created a new model.find method, which will attempt to find a model in the model.all collection whioch matches the supplied attributes
• Updated create method to use the find method internally

[braddunbar]

This seems like a good addition, though I think the merge functionality belongs in create. Gonna fix up the getByCid issue before merging. :+1:

[braddunbar]

Merged above and tweaked a bit in 8649210abc83c3c27e4149975ea45461e4e09e68. Let me know what you think!