add context levels to Partner#save tests
add test, cassette for #save with invalid attributes
disable rspec example profiling
refactor Partner hash update

Move response parsing and hash updating into a private method
"update_hash_from_response".  This is useful in that it can be
called after get/create/update operations.
add Partner.find(id)

Add Partner.find(id) class method.  Method instantiates a Partner
object and then invokes private methods to get data from the
back-end service and update the object state.  The Partner object
is returned on success.
raise exception when Partner not found

Add Rsbe::Client::RecordNotFound class.
Add code to raise Rsbe::Client::RecordNotFound when Partner.find fails.
Add cassette for case.
correct nesting of Partner.find examples
add Partner#update functionality

Add Partner#update examples, functionality, and cassettes.

Re-recorded other Partner#create cassettes because #save now includes
  a GET to determine if the save operation is a "create" or an
  "update", which correspond to a POST to the collection URL or a PUT
  to the item URL respectively
update README.md

Split user stories into Completed and Pending sections.