Find a place to host OCD documentation

[hancush]

Get the OCD core documentation up somewhere: https://github.com/opencivicdata

The OCD API documentation should also be taken down: https://ocd-api-documentation.readthedocs.io/en/latest/

[hancush]

I put the root docs up on RTD: https://opencivicdata-docs.readthedocs.io/en/latest/

[hancush]

I added both @derekeder and @fgregg as maintainers to the RTD project.

[hancush]

Now at https://opencivicdata.info/

[hancush]

OCD API docs deprecated, now point to opencivicdata.info

[hancush]

https://ocd-api-documentation.readthedocs.io/en/latest/