Many changes for implementing the goto task

Added getter functions for heading angle state in environment.py

Added subclass SARSALambda_LinFA_setAlpha  to learners.py that allows us
to set the learning rate applied to the heading angle states.

Implemented Randlov's goto task in tasks.py via subclass
LinearFATileCoding3456GotoTask.

goto_sarsalambda_linfa_replacetrace.py is the script used to execute the
training.
Merge branch 'master' of https://github.com/chrisdembia/agent-bicycle