[AIRFLOW-1384] Add to README.md CaDC/ARGO

added to  currently **officially** using Airflow:

[California Data Collaborative](http://californiad
atacollaborative.org) powered by [ARGO
Labs](http://www.argolabs.org)

Dear Airflow maintainers,

Please accept this PR. I understand that it will
not be reviewed until I have checked off all the
steps below!

- [x] My PR addresses the following [Airflow JIRA]
**https://issues.apache.org/jira/browse/AIRFLOW-13
84**

- The California Data Collaborative is a unique
coalition of forward thinking municipal water
managers in California who along with ARGO, a
startup non-profit that builds, operates, and
maintains data infrastructures, are pioneering new
standards of collaborating around and
administering water data for millions
Californians.

ARGO has deployed a hosted version of Airflow on
AWS and it is used to orchestrate data pipelines
to parse water use data from participating
utilities to power analytics. Furthermore, ARGO
also uses Airflow to power a data infrastructure
for citywide street maintenance via
https://github.com/ARGO-SQUID

- [x] My PR adds the following unit tests __OR__
does not need testing for this extremely good
reason:
Change to README.md does not require unit testing.

- [x] My commits all reference JIRA 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](http://chris.beams.io/posts/git-
commit/)":
    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"

Update README.md

added to  currently **officially** using Airflow
section of README.md

[California Data Collaborative](https://github.com
/California-Data-Collaborative) powered by [ARGO
Labs](http://www.argolabs.org)

Added CaDC/ARGO Labs to README.md

Please consider adding [Argo
Labs](www.argolabs.org) to the Airflow users
section.
**Context**
- The California Data Collaborative is a unique
coalition of forward thinking municipal water
managers in California who along with ARGO, a
startup non-profit that builds, operates, and
maintains data infrastructures, are pioneering new
standards of collaborating around and
administering water data for millions
Californians.

- ARGO has deployed a hosted version of Airflow on
AWS and it is used to orchestrate data pipelines
to parse water use data from participating
utilities to power analytics. Furthermore, ARGO
also uses Airflow to power a data infrastructure
for citywide street maintenance via
https://github.com/ARGO-SQUID

Closes #2421 from vr00n/patch-3

README.md

@@ -96,6 +96,7 @@ Currently **officially** using Airflow:
 1. [Bloc](https://www.bloc.io) [[@dpaola2](https://github.com/dpaola2)]
 1. [BlueApron](https://www.blueapron.com) [[@jasonjho](https://github.com/jasonjho) & [@matthewdavidhauser](https://github.com/matthewdavidhauser)]
 1. [Blue Yonder](http://www.blue-yonder.com) [[@blue-yonder](https://github.com/blue-yonder)]
+1. [California Data Collaborative](https://github.com/California-Data-Collaborative) powered by [ARGO Labs](http://www.argolabs.org) 
 1. [Celect](http://www.celect.com) [[@superdosh](https://github.com/superdosh) & [@chadcelect](https://github.com/chadcelect)]
 1. [Change.org](https://www.change.org) [[@change](https://github.com/change), [@vijaykramesh](https://github.com/vijaykramesh)]
 1. [Checkr](https://checkr.com) [[@tongboh](https://github.com/tongboh)]