fm's library has i2c support for the pcf8574 chip.
Most backpacks use the pcf8574; however,
when I looked at that i2c backpack a few weeks ago, I saw that it had
a mcp23008 on it.
The mcp23008 has different registers on it and works differently than the pcf8574
so fm's current library will not work with that backpack.
It isn't that difficult to convert pre 1.x code that uses the wire library to work with
It usually as simple as modifying a few calls like send() changes to write() etc...
Another option would be to get the adafruit i2c backpack library.
It uses the mcp23008. It will need modifications since the output port bits
in the adafruit board won't match the output port bits used on your board.