external library: auto-detection of system call based on current driver
Added tests
updated README
- external lib: solved incompatibility with biblatex's  \cite[][]{name}  	command

		(http://tex.stackexchange.com/questions/173465/tikz-error-for-externalized-graphics-but-output-is-correct}
improved message + updated todo
- fixed bug: \pgfplotstablenew can now overwrite existing tables.
updated todo
	- fixed bug: extra ticks near intersections of axis lines were hidden
added test
documented new number parser feature
added test