Add kwargs to plotting and fix 1D plotting bug

[TomSlater]

Added kwargs for all matplotlib plotting functionality.

Fixed bug in which 1D histograms would not display in new figure.

[codecov[bot]]

Codecov Report

Merging #63 (e6b2618) into master (5f51e63) will increase coverage by 1.35%. The diff coverage is 92.85%.

@@            Coverage Diff             @@
##           master      #63      +/-   ##
==========================================
+ Coverage   84.94%   86.29%   +1.35%     
==========================================
  Files          15       15              
  Lines         983      978       -5     
==========================================
+ Hits          835      844       +9     
+ Misses        148      134      -14     

Impacted Files	Coverage Δ
ParticleSpy/api.py	91.17% <88.88%> (+4.07%)	:arrow_up:
ParticleSpy/ptcl_class.py	86.25% <94.11%> (+6.83%)	:arrow_up:
ParticleSpy/tests/test_plotting.py	100.00% <100.00%> (ø)

[TomSlater]

This implements #48 .