Added discrete variable support for Metropolis and a BinaryMetropolis step function
Fixed bugs in BinaryMetropolis
Cleaned up discrete type support
Added discrete variable support for Metropolis and a BinaryMetropolis step function
Fixed bugs in BinaryMetropolis
Cleaned up discrete type support
Merge branch 'metropolis' of github.com:pymc-devs/pymc into metropolis

Conflicts:
	pymc/step_methods/metropolis.py