Aggregate fix with reversed zlimits
Merge pull request #327 from ChrisBeaumont/agg

Aggregate fix with reversed zlimits
Test coverage
typo
astropy v0.2 test fix
Image tests
layer artist model tests
Test failure fix
Merge pull request #328 from ChrisBeaumont/testing

Test coverage improvements
Speedups for image contrast scaling
Merge pull request #331 from ChrisBeaumont/image

Image contrast scaling speedups
PV aspect stretching
Merge pull request #332 from ChrisBeaumont/image

PV Aspect ratio stretching
Better autodiscovery of categorical data
PEP8
Merge pull request #333 from ChrisBeaumont/category

CategoricalComponent autodetection