Adds failing test to expose addMockModule bug identified in issue 764.
Adds failing test to expose removeMockModule bug identified in issue 764.
fix($protractor): removeMockModule bug identified in issue 764

Calling removeMockModule with a name that was never added would incorrectly remove the most recent
module added with addMockModule.
After this fix, a similar call results in a no-op.
fix($protractor): addMockModule bug identified in issue 764.

Calling addMockModule twice with the same module name added both modules and submitted each to the
browser for registration.
After this fix, calling addMockModule with the same module name twice removes the first module
from the list to be submitted and adds the new module to the end of the list.

Breaks $protractor.addMockModule, insofar as any code was writen that intentionally or inadvertently
depends on the old behavior.
docs($protractor): Updated addMockModule docs to reflect changes to behavior as a result of fixing issue 764.

Closes #764.