Replace raco submodule with install/develop

[bmyerz]

@senderista and I discussed removing raco as a submodule. The reason is 1) difficulty developing raco (replace submodule with symlink or keep changing submodule commit hash for raco...) and 2) that it would be nice to point myria-web deployment at releases of raco.

Workflow for deploying/developing myria-web without Raco hacking:

• pip install raco before running myria-web
• or cd raco; python setup.py install

Workflow for developing myria-web with Raco hacking:

• cd raco; python setup.py develop

[domoritz]

The problem was app engine, right?

[senderista]

Yes, it's been a while since I looked at this, but I think GAE restrictions on third-party libraries were the original reason for including raco as a submodule. We might be able to install it via pip using a lib directory under the GAE root directory: https://cloud.google.com/appengine/docs/python/tools/libraries27?hl=en#vendoring. Per the instructions on this page, we would add the following to appengine_config.py:

from google.appengine.ext import vendor

# Add any libraries installed in the "lib" folder.
vendor.add('lib')

Then we would add the desired raco version to requirements.txt and run pip install -t lib -r requirements.txt before deploying.