[FIX] TypeError: object of type 'BrowseRecordIterator' has no len() (fixes #5)
[FIX] Use the user context by default if it is not supplied in 'OERP.search()', 'OERP.create()', 'OERP.read()', 'OERP.write()' and 'OERP.unlink()' (fixes #6)