Make sure d3 super chart class gets included first
Add Barchart class for simple barchart
Add Visualisation for weighted historical exports per gdp

Visualisation for issue #66
use Barchart for this one
Realign a few styles; Barchart and explanation class

barcharts get a default style
explanation style will be global
Merge branch 'master' into 66-weapons-exports
Merge pull request #76 from okfde/66-weapons-exports

Schädliche Waffenexporte: Waffenexporte in nicht-demokratische Staaten, % of GDP