Generate state machine diagram in Mermaid Markdown

[alysivji]

Closes #4

Added a fsm_draw_state_machine command line script that takes in a workflow that inherits from StateMachine and generates a state diagram.

[codecov-commenter]

Codecov Report

Merging #12 into master will decrease coverage by 5.04%.
The diff coverage is 85.36%.

@@             Coverage Diff             @@
##            master      #12      +/-   ##
===========================================
- Coverage   100.00%   94.95%   -5.05%     
===========================================
  Files            5        6       +1     
  Lines           78      119      +41     
===========================================
+ Hits            78      113      +35     
- Misses           0        6       +6     

Impacted Files	Coverage Δ
finite_state_machine/draw_state_diagram.py	81.81% <81.81%> (ø)
finite_state_machine/state_machine.py	100.00% <100.00%> (ø)

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