Update: as of 14.10 utopic, there is a semi-working driver included by default, but it frequently disconnects and has difficulty reconnecting. The best solution is to continue to build the lwfinger driver as described below and then blacklist the driver included in Ubuntu.

That how-to link is outdated; the latest version of the rtl8723au wireless driver can be found at https://github.com/lwfinger/rtl8723au.

In preparation we'll need some build tools and kernel headers:

sudo apt-get install git build-essential linux-headers-generic linux-headers-$(uname -r)

Here are the steps to install:

git clone https://github.com/lwfinger/rtl8723au.git

cd rtl8723au/

make

sudo make install

sudo modprobe 8723au

When you update the kernel, you'll need to run these steps again to get wireless working (except for the git clone). To fetch the latest version of the code, use git pull. Alternatively you can set up DKMS to do that for you as described in user20826's answer.

The bluetooth driver for that chip can then be found at https://github.com/lwfinger/rtl8723au_bt. Perform the preparation as above and install like this:

git clone https://github.com/lwfinger/rtl8723au_bt.git

cd rtl8723au_bt/

make

sudo make install