New documentation and updated version number for npmjs
fixed issue where when adding a cell in a row not in sequence would cause corrupted excel data.
fixed issue where if a WorkSheet was added, but then no cells added, execution would stop
fixed issue where workbooks would cause MS Excel for Windows to crash on print preview
fixed issue where if undefined or 0 value was passed to cell or row function, execution would stop
added changelog
lib/WorkBook.js: refactored .write method to .writeToBuffer and .write

Thus one could get the buffer that was generated by xlsx before it would be written out. Which is useful for when one would want to write it out to an alternative stream.
Merge pull request #11 from agmen-hu/master

lib/WorkBook.js: refactored .write method to .writeToBuffer and .write
updated changelog and package.json to reflect pull request
Merge branch 'dev'

Conflicts:
	changelog.txt
	lib/Row.js
	package.json
	sample.js