Build is failing

[palnabarun]

While working on the other PR, I saw that the master's Travis build is failing. On further investigations, I found that they were failing due to change in how Altair interpreted inline data. The earlier behavior was to keep Inline Data as it is, but now they convert it into Named Data. This was breaking our tests as we did not have support for that.

Ref:
Altair Changelog
Failing Travis Builds

[palnabarun]

I also suggest adding a Travis Build badge to the Readme so that we know if a build is failing.

[tacaswell]

Adding using alt.data_transformers.consolidate_datasets = False is probably a good quick-fix.

How big of a change is it to adapt to the new scheme? It may be best to simply require altair 2.2.0+ and only support that.

[palnabarun]

I am okay with both the options, either specifying the consolidate_datasets flag or the project allows altair versions <= 2.1.0 .

However, since the support was needed at some point in time, I went ahead to put up a check for the availability of a named dataset. I pushed some modifications few minutes ago which checks if the dataset named is present or not.

One issue I am facing right now is testing the case when named data is specified but no dataset is passed on to altair.

[palnabarun]

Figured out the test case. Please have a look at the PR.