Enhance build to process API JSON files for Atom 1.0.0 and newer

[jasonrudolph]

This pull request targets the api-docs branch. (That branch is currently a work in progress. We anticipate opening a pull request for that branch soon.)

• [x] Pull in the API JSON files for all Atom versions from v1.0.0 to present (6ccef216df76f0c2dc7e0e595b49986706c91618)
• [x] Update Rake task to read from data/apis-by-version and not delete source files
• [x] Replace the split_api_json Rake task with some equivalent logic in gulpfile.js, so that npm run gulp continues to provide the end-to-end build process (42c10c6cf57f38bf9a1f109159d53a014b2b65a3)
• [x] Enhance the nanoc:compile task in gulp to avoid exceeding the max buffer size, now that our build now writes quite a bit more content to STDOUT

[jasonrudolph]

:wave: @lee-dohm: Here's what I'm working on for the API docs migration so far. If you see anything in here that seems like it's going in a different direction than what you had in mind, please let me know. :bow:

[lee-dohm]

Sounds like the right approach to me! 👍

[jasonrudolph]

:wave: @lee-dohm: I think this is ready for review now.

Note that the build currently fails when attempting to verify external links, but I anticipate us fixing that issue before we merge these changes into master. (This pull request targets the api-docs branch, so merging this pull request will not merge these changes to the master branch.)

[jasonrudolph]

:wave: @lee-dohm: I'm gonna go ahead and merge this branch, so that @as-cii and I can get started on the next steps. However, if you notice anything that you'd like to see changed, just let me know, and I'll be sure to take a look.