Tests for variable resolutions

[ageorgou]

We should extend the tests to check that the import of variable-resolution and -shape data (#36) works correctly. We've compared against MATLAB loading (e.g. 0e6f167) but should record the resulting signature and add this to the automatic tests.

We'll also need to subsample the data we have (fewer trials and ROIs) to get a smaller dataset we can easily check on Travis.

• Record signature for dataset we have (200228_14_15_57)
• Add to "long tests"
• Subsample the above dataset
• Add signature and create "short test" for subsampled data
• Add subsampled dataset to tar data so it runs on Travis