Adjust relative scaling of the axis (addresses #1)
Remove manual interpolation of axes in tests
Modify test to verify shifted axes
Change level to be within input range
Remove `Grid` requirement from tests
Delete REQUIRE

Don't need this any more!  For now...
Merge pull request #7 from tlycken/fix-axis-scaling

Adjust relative scaling of the axis (addresses #1)
Changes to travis script after recent dev ops