version 0.3.1

#15 #16 better support for datetime format

Version 0.3.0: improve performance

#13 Performance up: cache parsed nodes and use flyweight pattern for node.

version 0.2.2

#12 fix bug: treat some non-printable characters as whitespace

version 0.2.1

#11 fix value could be None, but error raised

version 0.2.0

prevent the registered namespaces from being polluted

Version 0.1.2

#6

version 0.1.1

avoid reference cycle

Version 0.1.0

Using f-strings(PEP 498) style literal string interpolation without Python 3.6.