Apply relevant changes from PeopleForBikes implementation

[KlaasH]

Tilegarden is being used in https://github.com/azavea/pfb-network-connectivity, but since this will be the first production deployment and project integration, we've decided to copy it over and develop it there, to facilitate making the changes necessary for that project without too much overhead from trying to maintain compatibility with a hypothetical general implementation. The plan is to do what makes sense over there then bring that work back into Tilegarden proper as lessons learned and guidance for what makes sense in a general-purpose architecture.

To that end, this will be a running list of changes made over there that should (or should not) be considered for incorporation.

Consider incorporating:

• [x] Convert import to require to be able to run in Node 8 without traspilation, remove Babel (see https://github.com/azavea/pfb-network-connectivity/commit/eb2dbe9c530a2b3d4c7fca02bcd112de87894c81)
• [x] Remove fs-promise in favor of the built-in util.promisify (see https://github.com/azavea/pfb-network-connectivity/commit/19e94edc250c828bab669f18112b1c0648d71c15)
• [x] Switch to an Azavea fork of claudia-local-api
• [x] Return a specific error when there's no default config (https://github.com/azavea/pfb-network-connectivity/commit/b071e83be00a432e642035a66647ab499ae625b0)
• [ ] Add function to extract and apply path parameters as filters (https://github.com/azavea/pfb-network-connectivity/commit/ada61195c57b2bd73a3fa1a81922ba7784b98cbb)
• [x] Refactor filtering functions to take parsed XML to avoid extra xml/js round trips (https://github.com/azavea/pfb-network-connectivity/commit/6701ce64ba6e380fcf95c147c29131ebaa929091)

Changes that are specific to PFB, not for incorporation:

• Remove utfGrid and vector code
• Change database environment variable names
• Remove DEV_/PROD_ environment variable munging (might be worth refactoring, but the PFB change won't be directly applicable)

[KlaasH]

More changes to incorporate:

• [ ] From https://github.com/azavea/pfb-network-connectivity/commit/b0defb3ba16c90880d68ccccc14b740021d03786:
  • [x] Switch to using Mapnik XML as the tracked, authoritative config
  • [x] Add optimization parameters to example XML configs
  • [ ] Change MML/CartoCSS conversion to operate as a helper utility (but not run automatically)
  • [x] Move database variable parameterization into the XML--i.e. fill from environment at runtime
  • [ ] Add database variables to Lambda environment
  • [x] Convert 'deploy' commands in package.json to scripts
• [ ] Add logger utility (https://github.com/azavea/pfb-network-connectivity/commit/2bb311733412871722c2384bd0ea6026326ad6ca and https://github.com/azavea/pfb-network-connectivity/commit/a20863b4aac65af9f3be96b8b220427079c75b8b)
• [ ] Improve organization of config files to facilitate multi-environment deployment (https://github.com/azavea/pfb-network-connectivity/commit/becd243d5c802db20f251e1257d0acaf6f43f59f)