fix misleading example for map function

the example used map(val,0,1023,0,255) to map a value from an analogue pin to 0-255 (probably copied/pasted from arduino).  this is misleading because analog pins actually return 0-4095), like the example now does
Merge pull request #80 from g-rocket/patch-1

Fix misleading example for map function
Merge branch 'master' into gh-pages