Fixed some text in README.md

[Marketionist]

PR Checklist:

• [N/A] I have run npm test locally and all tests are passing.
• [N/A] I have added/updated tests for any new behavior.
  
• [N/A] If this is a significant change, an issue has already been created where the problem / solution was discussed: [N/A, or add link to issue here]
  

PR Description

This pull request fixes some text to be more consistent in README.md

[Marketionist]

@mikeal @nylen @simov @FredKSchott please review and merge if ok

[Marketionist]

@mikeal @nylen @simov @FredKSchott please have a look

[nylen]

Seems fine to me. Thanks!