Repository is unexpectedly large

[ghost]

The GitHub API gives the size of the Norma repository as 362425 KB and the AMI repository as 301415 KB.

The recent experience of two new developers, both of whom needed to buy additional hardware in order to be able to clone and work with these repositories, suggests that new users or developers are unlikely to expect these repositories to be so large.

Ways of reducing the size of the repositories should be investigated. For instance, could the repositories' test corpora be factored out into a different module that can be shared, as a dependency, between Norma, AMI, and perhaps other modules in the AMI stack?

(Corresponding Norma issue: ContentMine/norma#71 .)