Bug 549786 - API doc parser and client-side renderer

This updates the "cfx docs" server-side API parser, to take an .md file and
turn it into a JSON data structure. The cfx docs server provides this JSON
over HTTP when asked for e.g. packages/jetpack-core/docs/url.md.json . The
client-side javascript now has code to render the JSON into HTML instead of
rendering just the markdown (e.g. docs/url.md), giving us nicely-formatted
API docs.

packages/jetpack-core/docs/url.md

@@ -1,47 +1,39 @@
-The <tt>url</tt> module provides functionality for the parsing and
+The `url` module provides functionality for the parsing and
 retrieving of URLs.
 
-<tt>url.**toFilename**(*url*)</tt>
-
+<api name="toFilename">
+@method
 Attempts to convert the given URL to a native file path.  This
 function will automatically attempt to resolve non-file protocols,
-such as the <tt>resource:</tt> protocol, to their place on the file
+such as the `resource:` protocol, to their place on the file
 system. An exception is raised if the URL can't be converted;
 otherwise, the native file path is returned as a string.
+@param url {string} The URL to be converted.
+</api>
 
-<tt>url.**fromFilename**(*path*)</tt>
-
-Converts the given native file path to a <tt>file:</tt> URL.
-
-<tt>url.**resolve**(*base*, *relative*)</tt>
+<api name="fromFilename">
+@method
+Converts the given native file path to a `file:` URL.
+@param path {string}
+</api>
 
+<api name="resolve">
+@method
 Returns an absolute URL given a base URL and a relative URL.
+@param base {string}
+@param relative {boolean}
+</api>
 
-<tt>url.**parse**(*url*)</tt>
-
+<api name="parse">
+@method
 Parses the URL and returns an object with following keys:
-
-<table>
-  <tr>
-    <td><tt>scheme</tt></td>
-    <td>The name of the protocol in the URL.</td>
-  </tr>
-  <tr>
-    <td><tt>userPass</tt></td>
-    <td>The username:password part of the URL; <tt>null</tt> if not
-    present.</td>
-  </tr>
-  <tr>
-    <td><tt>host</tt></td>
-    <td>The host of the URL, <tt>null</tt> if not present.</td>
-  </tr>
-  <tr>
-    <td><tt>port</tt></td>
-    <td>The port number of the URL, <tt>null</tt> if none was
-    specified.</td>
-  </tr>
-  <tr>
-    <td><tt>path</tt></td>
-    <td>The path component of the URL.</td>
-  </tr>
-</td>
+@returns {object}
+  @prop [scheme] {string} The name of the protocol in the URL.
+  @prop [userPass] {string} The username:password part of the URL; `null` if
+  not present.
+  @prop [host] {string} The host of the URL, `null` if not present.
+  @prop [port] {int} The port number of the URL, `null` if none was
+  specified.
+  @prop [path] {string} The path component of the URL.
+@param url {string}
+</api>