Add Dockerfile.release

[brendan-ai2]

• Ensures that the versions of allennlp and allennlp-semparse specified in requirements.txt/setup.py are compatible.
  • Corresponding build: http://build.allennlp.org/viewType.html?buildTypeId=AllenNLPHub_Release
• The existing dockerfile and TC build work only on the various masters.
• For Create allennlp-hub repo allennlp#3351

[brendan-ai2]

This enables the build I mentioned in my previous PR. Please take a look!

[matt-gardner]

I'm a bit confused about how the directory structure is set up (not sure how you can copy allennlp and allennlp-semparse as you do), but I'll trust you've done whatever magic is necessary in the TC build machine.

[brendan-ai2]

Sorry for leaving that unclear! Added comment:

# We expect that the various repos are checked out under a directory matching
# their name, e.g. allennlp-semparse. A TeamCity build can be configured to do
# this by adding the checkout rule "+:.=>allennlp-semparse". These are found
# under "Version Control Settings" -> "VCS Roots" -> "Edit checkout rules".

I've also modified the other Dockerfile to adopt a more typical structure so that this isn't required for the common case. (Since we're only installing packages.)

[brendan-ai2]

Thanks for the review!