Added trace slicing behavior to __getitem__ in NpTrace
Renamed types to vartypes
Fixed bug in trace slicing
Unified track and trace arguments to address #271
Brought multivariate disrtributions into main pymc namespace
test_slice now checks shape of trace rather than size
Merge pull request #277 from pymc-devs/traceslice

Added slicing of NpTrace objects
reduce size of Nat so that tests take shorter
fix discrete unif problem when using int64: no idea what its about, but we should fix it at some point
added knownfail
re-added missing (git add -p) dlogp check with numerical gradient
geweke test needed more samples
disabled parallel sampling
Unsatisfactorily resolved the test failures cited in comments of #269
Merge branch 'tests2' of github.com:pymc-devs/pymc into tests2