add discrete step method tests

Tests for discrete step methods were missing.
guess the scaling for only our variables

Nuts was guessing the scaling for all the variables, not just the ones
we care about.
got discrete step test passing
add support for variables > 1d in traceplot

traceplot would generate an error if a trace of a more than 1-d
variable was.

Now we ravel the dimensions after the first.

We should support for this in forestplot and autocorrplot.
Revert "BLD: Remove broken nose-timer."

This reverts commit 079a0c30e277e5776f4125f6b737394d34127162.
remote timer-verbose arg from travis commands
import checks with dot to avoid error in py 3.3
import models with .models for py 3.3
Merge pull request #521 from pymc-devs/timer

Misc: add back nose-timer, support multidimensional variables in traceplot, test discrete step methods