search with specific baseDN
search with specific baseDN

In the original activedirectory it was possible to specify baseDN on function findUsers, for example 

     ad.findUsers( {baseDN: 'OU=eastcoast,DC=company,DC=com'}, function(err, users) .......

In activedirectory2, this option was missing, it would only use the baseDN that was specified at new ActiveDirectrory(options).
This commit fixes that: if the search option specifies a baseDN then it is used, else it defaults to ad.baseDN.
jsumners/node-activedirectory