v3 finalized

• real life tested with several platforms (atmega, atsamD21, Atsam3x, esp8266, esp32, teensy)
• extend and fix hardware support (specially esp-boards, esp32, ...)
• added travis CI for a big bunch of controllers
• delayMicroseconds() hardware abstraction to allow proper nRF51-use (redbear messed up the delaymicroseconds()-implementation)
  • will be removed as soon redbear fixes its code
• overload write() to replace write_bytes() and read() to replace read_byte()
• update code documentation, doxygen style
• allow to use internal pull-up if micro controller has support for it -> most µC support INPUT_PULLUP in combination with pinMode(), others will get an error message or warning if feature is enabled but not supported / tested
• clean up compiler-switches
• better implementation to allow parasitic power to bus, otherwise master will act as open-drain-only! -> this was totally wrong before as the bus was powered for a short amount of time even if powering is disabled
• extend examples with ds2438 and a bus-discovery feature
• clean up examples, easier to understand, more similar to each other
• put hardware dependant code into platform.h
• better naming of variables and a lot of code cleanup
• simplify pin-access and interrupt-handling
• improve onewire class-interface (it was possible to copy the object, ...)
• reduce size of data types if possible, more const correctness and much more explicit code
• get rid of most ancient c and cpp code and reduce language mix
• decide on one code style - Allman braces - was closest to main style in original
• a lot of how-to documentation for this lib inside this readme