Adds zoom and centering parameters to DecoratedMaps and small PEP8 syntax fixes

## Changes

    * Moves zoom attribute to parent Map class.
    * Adds zoom parameter to DecoratedMap
    * Adds lat/lon parameters to DecoratedMaps to set the map center
    * Make code a bit more PEP8 compliant

## Why?

There was no way of generating a map like this:

http://maps.googleapis.com/maps/api/staticmap?center=33.402285,-111.942715&zoom=21&size=300x300&maptype=satellite&sensor=false&path=color%3ared%7Cweight:1%7Cfillcolor%3awhite%7C33.4022475,-111.9426775%7C33.4022475,-111.9427525%7C33.4023225,-111.9427525%7C33.4023225,-111.9426775%7C33.4022475,-111.9426775

I needed to be able to zoom and also place the center of the map wherever I wanted.

## How

I moved the zoom optional attribute only available in CenterMap to Map class since its a global maps parameter. Validation is done in the parent class and zoom can now be used in DecoratedMaps and CenterMap.

I also made some minor PEP8 syntax-style changes. Sorry for the single commit, it was a fast hack.