Issue #374: allow hyphens in class and guide names

This patch adds support for class and guide names which include hyphen
characters, which didn't work before for two reasons:

1. The jsonp generator wrote `Ext.data.JsonP.callback_name`, so a
   `callback_name` which included a hyphen wouldn't parse correctly. It
   now writes `Ext.data.JsonP["callback_name"]` so that any valid
   JavaScript identifier will work.
2. URLs for members in the generated documentation used the hyphen
   character to separate the class name from the member ID, so the
   website would be unable to parse URLs unambiguously. The separator is
   now the tilde character.
js-classes: add hyphens

This commit should *not actually be merged to master* -- it adds hyphens
to the names of built-in JavaScript classes in JSDuck's included
documentation, to conveniently demonstrate the fix for #374.
guides/: add a silly sample guide

Again, this commit should *not actually be merged* -- it adds a silly
guide for testing the fix for issue #374.