Changed the script so that QrCode can be instantiated many times using new
QrCode() instead of a global variable.

	modified:   README
	-> explained how to instantiate a QrCode, set a callback and
	decode it
	modified:   src/alignpat.js
	modified:   src/databr.js
	modified:   src/decoder.js
	modified:   src/detector.js
	modified:   src/findpat.js
	modified:   src/grid.js
	modified:   src/qrcode.js
	modified:   src/rsdecoder.js
	modified:   src/version.js
	-> changed everything that referenced the global qrcode variable
	to something passed in argument
	modified:    src/test.html
	-> changed the example to match to the new way of creating QrCodes
	-> added dashed border to canvas