Update google/debian:wheezy to use the latest packages, strip apt lists.

This change hooks into dpkg invocations to have them remove /var/lib/apt/lists/*_*.  This ensures several things:
1) The base image doesn't contain lists (these would often get stale and at 30Mb paying for them in multiple layers adds up)
2) When users utilize the idiom: "apt-get update && apt-get install -y foo" we strip the 30Mb of fresh lists it downloads.

NOTE: This will break users invoking "apt-get install" multiple times between updates.  These fall into one of two categories:
1) separate RUN commands: these should ALWAYS be prefixed with apt-get update due to docker's caching logic anyhow.
2) within a script: these will be unnecessarily forced to perform multiple updates, you can disable this behavior for a set of commands using:
```
mv /etc/apt/apt.conf.d/no-cache /etc/apt/apt.conf.d/no-cache.disabled
...
mv /etc/apt/apt.conf.d/no-cache.disabled /etc/apt/apt.conf.d/no-cache
```

This change also serves to simply update the basis, since the size of the "apt-get upgrade" is now ~40 Mb.