Merge pull request #4 from jhej/master

need grafikon 0.1.11 to have LaTeX work correctly
Merge pull request #5 from jhej/master

allow for adding more pgfplot options to plots
Merge pull request #6 from jhej/master

pgf plots improvements
png_medium output for gnuplot
cleanup; removing GP dependency
implemented axis limits for gnuplot
font sizes
(r)docs
many docs and some refactoring
gnuplot bar charts
removed duplicate points from diff series
mark size for gnuplot