Changing the 'scope' setting (for OAuth2) to be string instead of a list.

The OAuth2 url generated by gcalcli is invalid for me, changing the scope passed to it to a string instead of a list fixes it though.

Note that the API documentation for OAuth2WebServerFlow says that it should be a string:
https://google-api-python-client.googlecode.com/hg/docs/epy/oauth2client.client.OAuth2WebServerFlow-class.html