Added some unit tests related to help and the help menu

[tleonhardt]

Also:

• When running cmd2.py as main, enable use of IPython if present to aid with debugging and troubleshooting
• Deleted a unit test which wasn't reliable

[codecov]

Codecov Report

Merging #158 into master will increase coverage by 0.34%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #158      +/-   ##
==========================================
+ Coverage   89.45%   89.79%   +0.34%     
==========================================
  Files           1        1              
  Lines        1147     1147              
==========================================
+ Hits         1026     1030       +4     
+ Misses        121      117       -4

Impacted Files	Coverage Δ
cmd2.py	89.79% <ø> (+0.34%)	⬆️

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