C3: Set thickness of lines in timeseries & line charts

@seubert you can just increase the stroke-thickness on .c3-line - see this JSFiddle for an example :)

Thanks for answering that, @AnSavvides! @seubert — eventually this will be in the c3js.org API reference, which is something I plan to write documentation for this week.

_Edit:_ Actually, @AnSavvides, mind if I use your JSFiddle as an example in the reference? If not, could you please add a quick doc comment to your CSS, formatted like the following:

/**
 * masayuki/c3#808 — "Set thickness of lines in timeseries & line charts"
 * Example by github.com/AnSavvides, 2014
 * License: MIT
 */

Feel free to change the license from MIT to something compatible. Thanks!

Thanks, @AnSavvides and @aendrew ! Much appreciated.