Add Date Inequality Support

[JenniferMah]

Fixes

Checklist

• I acknowledge that all my contributions will be made under the project's license
• I have made a material change to the repo (functionality, testing, spelling, grammar)
• I updated my branch with the master branch.
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation about the functionality in the appropriate .md file
• I have added in line documentation to the code I modified

Contributing to Twilio

All third party contributors acknowledge that any contributions they provide will be made under the same open source license that the open source project is provided under.

Short description of what this PR does:

• Add date inequality support
• Convert API parameter DateSent> and DateSent< to CLI formatted flags.

If you have questions, please file a support ticket, or create a Github Issue in this repository.

[codecov]

Codecov Report

Merging #79 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff            @@
##           master     #79      +/-   ##
=========================================
+ Coverage   98.59%   98.6%   +<.01%     
=========================================
  Files          26      26              
  Lines         785     786       +1     
=========================================
+ Hits          774     775       +1     
  Misses         11      11

Impacted Files	Coverage Δ
src/base-commands/twilio-api-command.js	97.87% <100%> (+0.04%)	⬆️

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[childish-sambino]

LGTM