Better way to enable universe and multiverse

Instead of copying over a hardcoded file we just uncomment the correct lines via two simple sed commands.

Conflicts:
	image/sources.list
Upgrade from Precise to Trusty

Conflicts:
	image/sources.list
Migrate to Python 3

Ubuntu Trusty ships Python 3 by default, but not Python 2. Older versions already ship Python 3, so this change should be safe.
Remove /dev/log if it's a file a file.

Fixes https://github.com/phusion/baseimage-docker/pull/25
Modify defaults for syslog_ng to function properly

On 14.04 (trusty) there is nos no need to list all the modules since that was fixed.
No only that, listing them causes an error and it doesn't start.
modified setuser to use Python3 (default on 14.04)
Update Changelog
Update the README to say that we're on Ubuntu 14.04 now.
Document the new environment variable newline handling in my_init
Bump version to 0.9.10
Update URLs to Vagrant boxes
Use Ubuntu 14.04 as Vagrant box
Early in the my_init initialization process, do not overwrite already-defined environment variables by the ones in /etc/container_environment.

Closes GH-52.
Document release date of 0.9.10
The syslog-ng script should restore /dev/xconsole permissions because that's what the official init script does
Fix syslog-ng.

The system() source in the default syslog-ng config file does
not work in Docker because it tries to access /proc/kmsg,
which is not allowed due to Docker's privileges. We replace
it by a source that only reads from /dev/log.
Install `ca-certificates` package by default.

This is because we include `apt-transport-https`, but Ubuntu 14.04 no longer
installs `ca-certificates` by default anymore. Closes GH-73.
Changelog.md now explicitly mentions that the latest version is not yet released