Update All Classes to New Style

Subclasses all classes from `object` class to future proof.  Don't think it
should matter much.

Fixed indentation error in wp_proxy.py.  Updated commenting style where needed.
Changed Some Methods to Properties

Just in the HeaderParm object.
README.md Typos

Fixed typos in README.md.
Bug Fix in html2md

Was not properly building the `more` line in text when more-text was present.
The `more` keyword was still present when it should not have been.
Introduce Post Object

The post object serves to unify post structues between different XMLRPC methods.
First usage is with the getPost option processing.
Use Wordpress XMLRPC Methods for Posting

The `publishPost` and `editPost` methods in wp_proxy.py now use the native
Wordpress XMLRPC methods for posting.  To facilitate this, the new post data
class now builds a `wpStruct` in addition to the `metaweblogStruct`.

The old `buildPost` function is now gone, while the old `utils._convertTime`
function is now an internal method in the post class.  It is used to convert a
time string assignment to the `dategmt` attribute to an appropriate XMLRPC
DateTime object.