fixed license to LGPL-2.1

the license mentioned in README was still GPL
using PyArray_* accessor functions

rather than directly accessing the members of PyArrayObject.
this is necessary to switch to newer API-versions of NumPy
switching to new (non-deprecated) numpy API 1.7

so we get rid of errors...
cast PyCFunctionWithKeywords to PyCFunction

since the method-array is of type PyCFunction
Updated ChangeLog
Bumped version to 0.6