Normalize JSDocs

-   wrap comments at 80 columns
-   use Markdown, particularly single-tick inline code, and treble-tick
    block code fences.
-   omit empty @private docs, they are superfluous
-   @function to @method depending on whether the function uses `this`
-   use asterisk columns
-   use {string}, {number}, {boolean} lower-case value types.
Merge pull request #1358 from kriskowal/jsdoc-normalize

Normalize JSDocs