Integration tests

[luizirber]

While our tests are quite good, some things may be misleading. For example, SBT tests (including gather and others) use small trees, it would be good to have examples using genbank/refseq. At the same time, running these tests on Travis CI might not be possible (due to db downloading).

(I'm particularly bothered with #395, only one failing test seems way to good to be true)

Not sure what to do, tho: I don't want to spin CI infrastructure... Maybe use something like AWS CodePipeline (since the DBs are already in S3)?

[ctb]

seems like maybe there's a natural fit with dahak here, at least for the initial bit of running things - no? or: I was thinking of posting smaller SBTs (~5k?) made using the same process as the big ones (i.e. automating that whole process) and then checking them on Travis.

[ctb]

we could also use/abuse the binder infrastructure :)