Implement a back end using Node.js and Micro

[rriegs]

This first cut of the back end will expose a REST API implementing wiki content storage via the file system. Each topic will be stored in its own file in the data directory. The following routes will be supported:

• GET /: serve the contents of index.html
• GET /*: serve the contents of the file with the specified path
• PUT /data/:file: create or replace a file with the specified path
• DELETE /data/:file: delete a file

Created files may be topic content, images, or other embeddable data.

[rriegs]

The above commits implement the back end as described, but also permit PUT and DELETE to subdirectories of data (creating and removing enclosing directories as appropriate) and return reasonable status codes for various kinds of errors.

Some enhancements that could be made in the future are:

• Enabling POST to perform various additional tasks, such as moving or copying files
• Reimplementing PUT and DELETE in terms of POST so non-JavaScript HTML can interact with the back end as well
• Returning useful results (rather than an error) when trying to perform operations on a directory:
  • GET could list directory contents
  • PUT or POST could create an empty directory
  • DELETE could remove an empty directory

At present, URLs ending in slash result in errors because fs operations interpret these as paths to directories but expect only paths to files. It might be reasonable to strip the trailing slash or, alternately, to use the trailing slash to signal that a directory is expected (assuming the last bullet above is implemented).