Add more client delegate methods

One for customizing response parsing, one for
customizing request setup, and one for pausing
tasks by default.

Minor delegation-related cleanup and documentation
included.
Minor core client documentation
Fix existing client delegate method tests from adding 'shouldStart' method
Fix client delegate test helper method misnomer
Factor out helper method for client delegate method tests
Add tests for remaining client delegate methods
Merge pull request #25 from 3dna/peng/client-delegation-1

Expand client delegation #1

Adds more client delegate methods, as well as the
tests for them. Minor refactoring for existing
delegate method tests included. Minor
documentation included.