THIS IS AN UPDATE FROM MY PREVIOUS ANSWER, SINCE A LOT HAVE CHANGED IN ELEMENTARY FREYA
Note that this answer uses ppas, which isn't advisable in a elementaryOS set up. However, to my knowledge, there is not an alternative way to do this. Thus, the instructions.
This is how I managed to install bumblebee and the nvidia driver in elementary OS. Unfortunately, I am unable to properly install any version higher than nvidia-355. Every attempt to install nvidia official drivers or xorg-edgers drivers or any other driver different from the 355 ended up with black screen.
I was helped by the fact that I installed Timeshift in my machine. I would strongly encourage everyone to do that before trying to mess with the graphics driver. The funny thing is that I have done several installations of the driver in Ubuntu machines before, for some reason it is a lot harder to do it on elementary OS.
Only follow this instructions if you can afford losing everything in you machine, do it for your own risk, ok?
Run your first backup using Timemshift.
Install opengl stable ppa & the graphics-drivers ppa
For some reason the bumblebee package on the repos do not work properly, the deamon keeps turning off. There is no need to install xorg-edgers ppa anymore.
The solution I found is to use the opengl+graphics-drivers stable ppas.
sudo add-apt-repository ppa:graphics-drivers/ppa -y
sudo add-apt-repository ppa:oibaf/graphics-drivers -y
sudo apt-get update
sudo apt-get install bumblebee nvidia-355
Then you have to make sure the bumblebee.conf is properly set:
sudo nano /etc/bumblebee/bumblebee.conf
and add the modify as follows ( sourcesource ):
[bumblebee] section: after "Driver=" insert "nvidia"
[nvidia-driver] section: after "KernelDriver=" insert "nvidia-XXX"
[nvidia-driver] section: after "LibraryPath=" insert "/usr/lib/nvidia-XXX, /usr/lib/nvidia-331-updates:/usr/lib32/nvidia-XXX"
[nvidia-driver] section: after "XorgModulePath=" insert "/usr/lib/nvidia-XXX/xorg,/usr/lib/xorg/modules"
Where XXX is the nvidia driver you have installed, in the example: nvidia-355
In my case, a simple sudo service bumblebeed restart did the job, but you may need to restart.
If anyone managed to install bumblebee with later drivers, please report how you did it in the comments and I may update this answer. It seems that gala won't work with later version in my tests.
