Now exports a constructor

The contructor takes an optional "options" parameter. The "options" parameter can take one argument named "arrays" which is an array of string containing the name of the desired fields that have to be deserialized as arrays. The deserialize overload is now taking only two parameters: (string, callback).
Merge branch 'master' of https://github.com/formix/damn-simple-xml

Conflicts:
	damn-simple-xml.js
	test/test-dsx.js
Updated a test to take account of system dependent newline