0.21
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"show" now works; files are still output if specified
---
0.20
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better warnings for incomplete data in "plot"
"plot" can plot with "twinx" when data is given in array or hash form
"tick_params" is removed from plt methods
fewer "my" for error arrays, using empty arrays from earlier; should increase efficiency slightly
added tests for twinx in plot for both array and hash variants
