[easy] README file does not show attributes of transactions

[jseutter]

The readme file does not show attributes of transactions. The transaction.payee thing is confusing for users because it is the "name" field in the ofx file. At least document it in the readme and maybe make it available as a name attribute on the Transaction object as well.

[malikoth]

Another issue with documentation: ofxparse.py:136-139 define the account.number property, which according to the comment, will be removed when OfxParse reaches v1.0 in favor of the account.account_id attribute. However, the README only tells new users to use account.number, and doesn't mention the account_id attribute. Shouldn't the README document how to access that information via the name its going to use in the future?

[cilynx]

This can probably be closed given #138.