Set eurostat_url as an option when package starts

[paulrougieux]

As discussed in #123

Set the option only if it is not already set, inspired by dplyr:
https://github.com/tidyverse/dplyr/blob/bbcfe99e29fe737d456b0d7adc33d3c445a32d9d/R/zzz.r

[antagomir]

Some travis checks not successfull. I did not find the explanation yet. https://travis-ci.org/rOpenGov/eurostat/jobs/421445589

[paulrougieux]

Related issues could be random error happening with apt get calls:
travis-ci/travis-ci#8507
and
travis-ci/travis-ci#9112
Can you relaunch the travis build?

[paulrougieux]

This travis job ran successfully https://travis-ci.org/rOpenGov/eurostat/jobs/421445590
And this one failed https://travis-ci.org/rOpenGov/eurostat/jobs/421445589
The funny thing is that they are both based on the same commit: 7ade7ae

[antagomir]

Yes I had noticed those points too.. but relaunching the build magically solved the issue. Merging.

[antagomir]

Next time perhaps desirable to make the pull request to the devel branch. I agree that this has not been clearly instructed anywhere.

[antagomir]

.. and many thanks!

[paulrougieux]

OK

Next time perhaps desirable to make the pull request to the devel branch.

Sorry, I didn't know about the devel branch.

I temporarily patched the code for a colleague who uses the package to collect data.
Can you please notify us here when the eurostat package is updated on CRAN?