Minor implements

[amoodie]

A few minor implementations.

• add ability to pass kwargs to colorbar instantiation in plot._append_colorbar use. This is helpful for specifying e.g., tick label formatter for plots. Adds test.
• implement the from_array pathway for ChannelMask. Update tests.

progress on #47

[codecov]

Codecov Report

Merging #51 (baa9d0c) into develop (8a56acb) will decrease coverage by 0.06%.
The diff coverage is 85.71%.

@@             Coverage Diff             @@
##           develop      #51      +/-   ##
===========================================
- Coverage    87.51%   87.45%   -0.07%     
===========================================
  Files            9        9              
  Lines         2403     2423      +20     
===========================================
+ Hits          2103     2119      +16     
- Misses         300      304       +4     

Impacted Files	Coverage Δ
deltametrics/plot.py	89.07% <0.00%> (-0.65%)	⬇️
deltametrics/mask.py	87.43% <100.00%> (+0.10%)	⬆️
deltametrics/io.py	87.77% <0.00%> (+0.27%)	⬆️

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