Fixes #170
Merge pull request #176 from rokroskar/master

initial travis ci setup
updated travis ci badge

[skip ci]
Update .travis.yml
Update .travis.yml

[skip ci]
added edgecolor keyword to velocity_image -- using non-black vector color and black edgecolor can result in poor quality pdfs
can't have multiple definitions for array mappings
Added vphi: command not found and vtheta: command not found to derived arrays
Merge pull request #175 from pynbody/beta

Fixes #170
Attempt to fix issue #179
Nosetest for issue #179 underlying problem
Correct behaviour when interpolated images are actually only using one level of interpolation - issue #172
Merge pull request #180 from pynbody/issue_179

Fix for issue 179 - new SimArrays based on IndexedSimArrays forget their context
Revert erroneous change to upper limit of smooth_range
Merge pull request #181 from pynbody/issue_172

Correct behaviour when interpolated images are actually only using one level
Fix issue #182
Remove -ftree-vectorizer-verbose=1 from cc arguments: latest versions of clang give an error as they do not recognize this flag
Second attempt to fix issue #182 - Profile fails when some bins are empty and derived arrays are required
Move all SPH content into sph submodule
Improve spherical image rendering using latest version of healpy