Reorganization of the spec

[thekaveman]

This is a proposed reorganization following up on #5

I am totally open to suggestions, renames, etc. (I used provider and agency but other options include operator and municipality for example).

There were no substantive content changes introduced. Some language was restructured, or edited for brevity or generalization. Some additional minor normalization of field names crept in as well.

I opted to organize components using folders, with a README.md file in each that contains that portion of the spec. My thinking was this would allow for additional files per component (e.g. an example .json data file). Another option is just a provider.md and agency.md file in the root.

[hunterowens]

This LGTM. @LADOTBikeshare @toddapetersen @thecorconian @xxmarcelxx?

[thekaveman]

An even simpler option is the single mobility-data-specification.md file we had before, but with these renames.

[hunterowens]

Merging