Set http user-agent when running Travis CI and AppVeyor

[kakirastern]

Fixes #1281.

Create environment variables in the astroquery/tests/test_internet.py files for both the Travis CI and AppVeyor, and then checked these are turned on in the respective .travis.yml and appveyor.yml .yml files by default. Finally, the http user-agent is changed in astroquery/tests/test_internet.py.

[codecov]

Codecov Report

Merging #1394 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1394   +/-   ##
=======================================
  Coverage   64.56%   64.56%           
=======================================
  Files         157      157           
  Lines       12228    12228           
=======================================
  Hits         7895     7895           
  Misses       4333     4333

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[bsipocz]

You still need to change the Agent pending on the new variable.

[kakirastern]

Thanks @bsipocz! Now, I see... Since by default the env variable CI=true, TRAVIS=true, and APPVEYOR - True, so I don't need to set these again in the .yml files. I will change the user-agent next.

[bsipocz]

#1307 has addressed this, it was just not xref-ed back to the issue.