Pin all libraries

[aittalam]

Some of the libs we use (e.g. HF evaluate) depend on other libs which are not direct deps for us without pinning them (in the specific case of nltk, evaluate does not even include it as a dep but will just warn you to install it if you try to use e.g. meteor without having it installed). As a result, we cannot guarantee stability (the nltk case made this evident).
To fix this, we should test our code to make sure our current set of dependencies is stable and then pin all dependencies, even indirect ones.