Made graph.size private, fixed bug in SetColors for 6 vars, better ti… …mescale for quickstart

added Begin() function to handle Serial.begin and storing milllis(). … …Avoid calling default constructor twice, was exhibiting undefined behaviour on copy to global plotter. Left duplicate calls in default constructor for the sake of backward compatibility

compatibility issues with dtostrf... switching to print 

missed one 

Merge pull request devinaconley#5 from devinaconley/listener-overhaul Listener overhaul (v2.1.0)

readme fix 

more updates to readme 

auto-scaling added. support for X-Y graphing added.