• Made python/perspective a lerna-ized package, such that yarn need not be invoked when building for Python from the repo itself.
• Made zerorpc and bufferutil peerDependencies which are installed when node_modules is not detected during setup, rather than hard deps of package.json. The perspective-python-node module will no longer fail the python build.
• Moved C++ assets to python/perspective/dist, and fixed clean and build scripts to reference this. A future PR should refine this approach even more, eventually copying all python assets here as well.
• Merges Typescript and Babel eslint configs, such that phosphor, jupyterlab and perspective-python-node all hav econsistent lint rules.

Also fixes #701