Actually, I2C support is compiled into the Wheezy kernel, but is blacklisted in the boot, as it isn't needed by the normal user. Removing that blacklist entry, and adding a modprobe for i2c-dev will create the /dev/i2c-0 device. Installing i2c-tools provides a high-level view of the I2C interface.
The command sudo i2cdetect 0 will show the 8x8 matrix attached to the system as device x'70'. I just have no idea how to use /dev/i2c-0 from that point to use the display. Actual documentation for the I2C Backpack and its supported command structure would go a long way to making the device usable on the Raspberry Pi. At this point it is not an electronic problem, just one of documentation.