[WIP] refactor: allow validated json to be automatically inserted into markdown files to improve consistency

[bkp7]

I have implemented the changes required to achieve inserting validated json into md files as part of the publish process per #417:

• I've moved the versioned md files from gitbook-docs to docs/src
• during the build process a copy of the md files is put into docs/github/_build
• all automated processes for documentation are run in the _build folder ( inserting version no, create changelog, etc + NEW json insertion with mdInsert)

Take a look at package.json which has been modified to accommodate this change.

The ONLY .MD document I have actually changed (so far) in order to illustrate the process is notifications.md. I have tried to keep the final built version as near as possible to the current version, so it is easy to do a diff between the old and the automated versions to check all changes have been made correctly.

To get going with this, update npm with npm install then create all md docs with npm run docs:prep

I believe I have made all changes necessary in the publishing tool chain. It is WIP in that all bar one of the md files still need to be altered to pull in json.

[bkp7]

This PR failed testing, However Travis CI has had some outages since 16 Jan 2018 18:10 UTC https://www.traviscistatus.com, and still ongoing at time of writing this. Nevertheless, the test showed as 'failed' not 'pending' although all tests do pass on my development machine running node 8.9.4 and npm 5.6.0. I have added ver 8 of node_js to .travis.yml just in case it's a version issue.

I'll investigate further once Travis CI is running reliably.

[bkp7]

It was my code: OK on Windows but not Linux.

Also this PR wont test OK with node-js v6 so I'm now going to test only with node-js v7

Now fixed.

[bkp7]

Travis conflict resolved.

[bkp7]

I am working on a neater approach for inserting stuff inline rather than having to create a 'compiled/new' md document - watch this space