Chart label formatting (conditional time format, shorter date format)

This is an attempt to make the chart labels user friendlier:

a) The dates in the stacked bar chart are displayed as 'Mon-DD' rather than 'YYYY-MM-DD'
b) The times in the line chart are displayed with 1 decimal if the total range is less than 3 or as integers if the total range is greater or equal to 3.

You can check the live demo (http://ec2-107-22-23-153.compute-1.amazonaws.com:3000/nodes) to see the results. There are 2 nodes, one has run times < 3, the other one > 3.