queue multiple alert messages
made alert modal a little nicer
passing dw.backend reference to visualizations
added alternative notification system for vis warnings
showing more helpful notifications
js build
refactored vis.warn to vis.notify
js.build
prevent same message from being alerted multiple times
line chart: notification about labeling of too many lines
pie chart: notification about grouping into others slice
styling of chart notification
changelog
Merge branch 'develop' of github.com:datawrapper/datawrapper into develop

Conflicts:
	www/static/js/dw-2.0.min.js