[#42] Change reference to airflow to Apache Airflow

[r39132]

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GitHub Issue

Fixes #42

Checklist:

• This pull request updates the documentation
• This pull request changes library dependencies
• Title of the PR is of format (example) : [[#14] Add Issue Template #17] Add Issue Template

What is the purpose of this pull request?

Updates Readme documentation.

How was this change validated?

N/A

Commit Guidelines

• My commits all reference GH issues in their subject lines, and I have squashed multiple commits if they address the same issue. In addition, my commits follow the guidelines from "How to write a good git commit message":
  1. Subject is separated from body by a blank line
  2. Subject is limited to 50 characters
  3. Subject does not end with a period
  4. Subject uses the imperative mood ("add", not "adding")
  5. Body wraps at 72 characters
  6. Body explains "what" and "why", not "how"

[praveen-kanamarlapudi]

LGTM

[praveen-kanamarlapudi]

Can you rebase from develop branch?