BUG: change assert.equals to a quick version of 'almost equals'
BUG: make paths continue if they include Inf values

even if Inf is only present after transformation, eg plotting 0 on log-scale.
Closes #248
BUG: make default matplotlib backend work on travis-ci
merge aflaxman-inf_and_log_zero_bug, regenerate min.js
Merge branch 'aflaxman-inf_and_log_zero_bug'