npm release v0.5.4

Setting tag.updateInterval has no effect if no change in value

* test of age of last update now uses relative tolerance (15%)
* tag.setUpdateInterval() now does not call API if no change

npm release v0.5.3

Introduces automatic tag updater plugins and other changes

Summary of changes:

• Created tag updater plugin class that uses polling (via a SOAP API endpoint). Includes full documentation.
• For demonstration, also created a tag updater with same core API signature that uses builtin interval-based update.
• Created literate markdown tutorial for using a tag updater.
• Converted tutorial to literate JS in markdown. Executable JS is auto-generated from literate markdown tutorial.
• Now auto-deploying npm releases through Travis.
• Other minor changes/fixes:
  • Some updates / improvements to documentation.
  • Adds new custom error class for unauthorized access error.
  • Leave error logging to client/user as much as possible

npm release v0.5.2

Release v0.5.2 on npm.

This includes a starting point of JSDoc documentation and generation of
online documentation.

Summary of changes:

• Setup for auto-deploying npm releases through Travis
• Setup for generating HTML documentation from JSDoc comments, and first
  vesion of online documentation. (Also offline in repo, but not npm.)
• Nearly complete platform object doc (except custom Errors)
• Streamlines and fixes update loop code for tags.
• Adds dbid property mapping for tag manager object.