docs: run .md files through grammarly

[redbrickone]

I left out the CHANGELOG.md but I can quickly run this through Grammarly if needed.

Closes #110

[SendGridDX]

All committers have signed the CLA.

[codecov]

Codecov Report

Merging #111 into master will decrease coverage by 3.29%.
The diff coverage is n/a.

@@           Coverage Diff            @@
##           master    #111     +/-   ##
========================================
- Coverage      88%   84.7%   -3.3%     
========================================
  Files           4       3      -1     
  Lines         175     170      -5     
========================================
- Hits          154     144     -10     
- Misses         21      26      +5

Impacted Files	Coverage Δ
lib/Client.php	81.56% <0%> (-3.76%)	⬇️
lib/Exception/InvalidRequest.php

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[thinkingserious]

Hello @redbrickone,

Thanks again for the PR!

It's HACKTOBERFEST! We want to show our appreciation by sending you some special Hacktoberfest swag. If you have not already, could you please fill out this form so we can send it to you? Thanks!

Team SendGrid DX

[thinkingserious]

Please add the CONTRIBUTING.md. Thanks!

[thinkingserious]

Hello @redbrickone,

Thanks again for the PR!

We noticed that you have earned 3 out of the 5 points needed to receive glorious SendGrid Hacktoberfest swag.

Please take a moment to checkout this link to find more issues to get you past the required threshold.

Also, please be sure that you have officially registered here.

Thank you and Happy Hacktobering!

Team SendGrid DX

[thinkingserious]

Hello @redbrickone,

Thanks again for the PR!

You have earned 3 out of the 5 points needed to receive glorious SendGrid Hacktoberfest swag.

Please take a moment to checkout this link to find more issues to get you past the required threshold or to simply continue the celebration.

Also, please be sure you have officially registered with us here by November 1, 2018 to qualify.

If you have any questions you can email us at [email protected].

Thank you and Happy Hacktobering!

Team SendGrid