Add env. var., command line options to worker files.
Fix argument+environment launching and test worker.
Final improvements to testing new features.

This commit

+ documents how to use TAG, ARGUMENTS, and ENVIRONMENT
  arguments to the CMake remus_register_worker function,
+ fixes the unit test so that it waits for the worker to
  exit properly instead of hanging,
+ uses a cross-platform sleep in the unit test.
Accept "WorkerName" tag in JSON worker file.
Remove debug stuff from test, fix WorkerName.
Avoid failures on Mac OS X 10.10 + boost 1.50.

Lexical cast throws exceptions when converting from strings to UUIDs;
use the UUID string_generator to do the conversion instead.
Merge pull request #184 from vibraphone/worker-factory-options

Worker factory options