change DifferentialExpressionResults.scatter default plotting style to have
linewidths > 0. Previously, using linewidths=0 cause plots to show up blank
in IPython Notebook on Mac
v0.5 marks a major improvement and maturation of metaseq but at the expense
of backward-compatibility. The changes are too numerous to list, but include
massive plotting improvements, speedups, more flexible API, and much more.