Added these use cases

• $$('div', '#context') Find within a context
• $$('#context').$$find('div') Find within a context (alternative syntax)
• $$.clear('div', '#context') Invalidates query on the context
• $$.clear(null, '#context') Invalidates all queries on the context
• $$.clear() Invalidates all of the cache
• $$.fresh('div', '#context') Shortcut for $$.clear('div', '#context') $$('div', '#context')