Bug with encoding for ETrade

[emin63]

Thanks again for this great software.

ETrade gives me an OFX file which has a line like

ENCODING:USASCII
CHARSET:NONE

which triggers a bug in ofxparse.py at https://github.com/jseutter/ofxparse/blob/master/ofxparse/ofxparse.py#L128.

I suggest adding something like

    elif cp == 'NONE':
        encoding = 'cp1252'

before the else clause in that area.

Let me know if you would prefer I make a pull request for this.