Update .travis.yml

[Nagesh A T (nageshlop)]

Add support for architecture ppc64le. This is part of the Ubuntu distribution for ppc64le.
This helps us simplify testing later when distributions are re-building and re-releasing.
The build and test results are available at the below location.
https://travis-ci.com/github/nageshlop/azure-storage-python

[Nagesh A T (nageshlop)]

Hi,
Could you review this request.

[Xiaoxi Fu (xiafu-msft)]

Thanks for the pull request! It looks great

[Nagesh A T (nageshlop)]

Hi Xiaoxi Fu (@xiafu-msft)
Thanks for considering the request. Could you help to merge changes.

[Codecov Comments Bot (codecov-commenter)]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 86.98%. Comparing base (4306898) to head (621d481).
⚠️ Report is 4 commits behind head on master.

Additional details and impacted files

@@ Coverage Diff @@## master #685 +/- ##
==========================================
- Coverage 87.05% 86.98% -0.07% 
==========================================
Files 52 52 Lines 5308 5288 -20 Branches 570 566 -4 ==========================================
- Hits 4621 4600 -21 
Misses 515 515 - Partials 172 173 +1 

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