Fix for loss of user-defined settings when calling begin()

[nuhash]

Moved initilisation to constructor so that user defined settings are preserved when calling begin()

Made to address #27

[CAP1Sup]

I created my own fork and merged your changes into it. Unfortunately, I don't think that Sparkfun is going to continue to update this repo. I'll do my best to keep mine up to date. I know that I could just use your branch, but there are other issues, such as the flaw in the temperature reading processing