Added dynamic default normalization.

[fabro122]

I implemented this, because I had myself the problem, that even though I tested many different normalization factors the program never seemed to work. Only after cloning and debugging step by step I was able to tell, that the norm-factor was still at fault. Therefore I implemented the following:

• By default the normalization-factor will now be calculated in each loop as the length of the (x,y,z)-vector from the accelerometer
• If the argument '--normalization-factor' gets supplied, it overrides this new default

You can see this pull request as a proposal. If you don't like it, just ignore it or ask for changes. If something is wrong with this pull request, feel free to call me out (this is my very first one).

[efernau]

I like this feature.

[fabro122]

I corrected the formatting, so it should hopefully work now