Add test case for nested args with multiple=True

verifies #29
Fix parsing of nested args when multiple is True

Add test cases for core.get_value usage with dict and
multiple implementation of MultiDict

resolves #29
Merge branch 'fix-nested-multiple' into dev
Update changelog and bump dev version
Add test case nested multiple args in tornado
Bump version -> 0.9.1
Fix multidict test on py26