Update readme to reflect changes with use command

[JenniferMah]

Fixes

Checklist

• 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:

• Update readme to reflect changes with use command

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

[codecov]

Codecov Report

Merging #29 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master      #29   +/-   ##
=======================================
  Coverage   98.42%   98.42%           
=======================================
  Files          22       22           
  Lines         570      570           
=======================================
  Hits          561      561           
  Misses          9        9

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