Just got my Arduino last night
Then, might I respectfully suggest that library development NOT be your first project?
If you are to persist in this endeavor, look at some other libraries. There are some things you need to consider.
The IDE creates a main() function, and calls init(), setup() and loop(). Somewhere in that process, it also calls any constructors that the sketch calls for.
Does your constructor get called before init() or after it? If you don't know, then you should not be writing code that relies on it having been called.
If your constructor is called first, and the mode of some pins is set, and then init() is called, and the mode all set to INPUT (the default), your code will not behave as expected.
You'll notice that a lot of libraries provide a begin() method, like Serial.begin(), EthernetClient.begin(), EthernetServer.begin(), LiquidCrystal.begin(), etc. The reason is that the constructor simply records what pins you want to use. The begin() method is where the calls to pinMode() go.
Since the begin() method is typically called in setup(), though it can be called in loop(), the begin() method(s) call(s) to pinMode() are guaranteed to be made AFTER the init() function has run, and therefore the effects are persistent.