Small typos in program description and very cosmetical fixes

I think it is a kind of important because users see the description on ./thermald --help.

temerature -> temperature
sensor -> sensors
best -> the best
decide -> decides
temrature -> temperature

This is not included in the patch, but I think that 
"Thermal monitors all temperature sensors ..."  -> "Monitors all temperature sensors"
sounds slighly better.

Also some very long lines were splitted on two.