Adding Transifex Client config file.

[zarembsky]

• [x ] Have you followed the guidelines in CONTRIBUTING.md?
• [ x] Have you checked to ensure there aren't other open Pull Requests for the same update/change?
• [x ] Have you added an explanation of what your changes do?
• [x ] Does your submission pass tests?
• [x ] Did you lint your code prior to submission?

[jsignanini]

@zarembsky looks like there's a tx init command that needs to be run to set up the tx command line tool. Please add instructions on how to set this up.

[jsignanini]

@zarembsky On second thought, since we're a public repo now, let's not add these instructions to the README since it will be misleading to a user that's not part of our internal dev team. Let's just undo all README.md changes.