Add optional assertion for checking against power-on reset values

[amotl]

Hi Robert,

this is a non-invasive variant to #8. If this does not make any sense, feel free to close it right away.

With kind regards, Andreas.

[robert-hh]

The major advantage of this method is, that the user does not have to know the critical value. But error handling must still be done in the user code. What is the real difference to adding a note in the documentation? P.S.: About golden handles: I could drop the method rankine(). It is too exotic.

[amotl]

The major advantage of this method is, that the user does not have to know the critical value.

That was just the idea of that, right. I am not sure if it was worth the effort. But as you also added some golden handles, I thought adding a silver one would do no harm ;].

So, feel free to close this and add it to the documentation.

Cheers!

[robert-hh]

Hi Andreas, I added the DS18X20Single class, dropped rankine() and added a warring in the documentation about 85°C as an initial return value.