Merge pull request #26 from oroulet/master

support string as arg to get_node
fix ref. count in variant converter
unify python 2.7 and 3.4
Merge branch 'master' of https://github.com/FreeOpcUa/opcua-python
clean def_readwrite + conversion
ref. count fix
Merge pull request #27 from mdcb-gmt/master

back to commons
expose namespace methods, add tests