Issue #129: Add client side for chroma server processing

* Changed up AidedColorDataBuilder to subclass BasicColorDataBuilder instead of FullScanColorDataBuilder
* Changed color.py to use ThinColorData/AidedColorDataBuilder/ChromaBlockchainState based on a key (for now default)
* Added chroma.py in services as the client to a chroma server (note prefetch isn't used yet)
* Added web.py to the setup.py
* Changed run.py on the server to be a little cleaner
Merge pull request #134 from jimmysong/129

Issue #129: Add client side for chroma server processing