Fix inherited queries when accessing cursor by index

Now the document class will be set correctly in code like this::

    doc = cursor[3]
Updated unit test
Merge pull request #148 from asivokon/master

Inherited queries are now supported when accessing cursor by index
changed the namespace on schema document errors
Merge pull request #153 from rtjoseph11/master

changed the namespace on schema document errors
fixing typos within README.md
Merge pull request #158 from 1123/master

fixing typos within README.md
Merge remote-tracking branch 'upstream/master'

Conflicts:
	setup.py