First version of a line chart and a multiples line chart

can add a single line chart for a country or multiples (all countries at
once)
Add grid lines
Add y-axis to the left side; mark germany

add y-axis to every fifth element so that it is displayed on the left
side of the charts
add red color to germany
streamline grid and y-axis
get charts more breathing room
Refactor LineCharts common functions into class

introduce new class for line charting
add important methods into it
extend peacekeeping class from it
Add international mean data to graphs
Add tick option

use tick option for axis
add it to options object
Add setData and setDate keys to lineChart

add defaults for data (value) and date(date) keys
Add render function to linechart

add createYAxis to add yAxis to graph
overwrite render function from d3graph class
Overwrite draw function and add lineClasses

overwrite default d3graph class draw function
add set line class and line class for element functions
Add MeanLine to graph

add MeanLine for data as default
Uses invisible Voronoi tessellation for mouseover

the closest point to the mouse on any line is highlighted
http://bl.ocks.org/mbostock/8033015
add circle for „selected“ point
Use new linegraph functions to show peacekeeping data

add mouseover highliting and point selection with value display of line
and point
uses Voronoi tessellation to handle mouseover
http://bl.ocks.org/mbostock/8033015
Style peacekeeping viz
Add link to peacekeeping, fix link to exports
Remove mixins; not yet ready
Move data to different folders and update the paths
Merge pull request #69 from okfde/peacekeeping

Peacekeeping Visualisierung
Merge branch 'master' into weapons-overview

Conflicts:
	source/sicherheit/index.html.haml