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Show me a chart.
Store "good" fixture chart images.
Testing: compare known good chart images with current versions.
More test cases.
I have four CPUs.
Merge branch 'testies'
Travis.
Ensure screenshots are the correct dimensions.
Allow a little difference between systems.

The fixtures are created on my machine but Travis's generated
screenshots don't *exactly* match - one of the tests returning a
difference of 4. This seems to be an acceptable range.
Travis badge.
Might as well make Travis run that bit faster.
Merge pull request #35 from benpickles/travis

Travis CI
Do this once.
Let me pass options to Mocha bin.
Better test runner feedback.
Fixes #33 without causing #34.
Cope with Travis rush hour.
A couple more test cases for when a bar chart's values are all the same.
Merge pull request #36 from benpickles/fix-all-zero-bar-chart-properly

Fix all-zero bar chart properly