Update pinned versions in requirements files

[ngreenwald]

Is your feature request related to a problem? Please describe.
We currently have extremely specific version requirements for many of the dependencies in our project. In general, these are not there for a particularly good reason, but instead because that version happened to work.

Describe the solution you'd like
We should specify ranges of compatible versions rather than specifics where possible. This will likely require some trial and error of testing out expanded ranges of allowed packages and seeing when things fail in Travis or the docker.

Additional context
A good starting place would probably be the ranges that are specified in deepcell-tf