2.1.2 Fixes Serial print issue

Fixes #18 by adding the requirement for #define _HTDEBUG to use the serial. Example is updated

Fixes print warnings

• Propagates fixes in #16

Character display, print celsius

Merge pull request #13 from valerionew/character-display

Character display

Fixes for the leading zeros problem

See #7 and #8

Now zeros are correctly represented for values < 1

Fixed keyword separator bug

Thanks to @per1234 for #5

The Arduino IDE requires the use of a single true tab separator between the keyword name and identifier. When spaces are used rather than a true tab, the keyword is not highlighted.

Reference:
https://github.com/arduino/Arduino/wiki/Arduino-IDE-1.5:-Library-specification#keywords