Scaled bar width fix

[johnw86]

Add logic for calculating bar width when ticks are less than the data labels

Issue: #2323

[coveralls]

Coverage decreased (-0.03%) to 71.905% when pulling 87966a1 on johnw86:master into 8e37b81 on nnnick:master.

[etimberg]

Merged. Thanks @johnw86

[mealy]

One Note - this fix only helps the non-stacked cases.
To fix the same problem in stacked cases you have to also modify categoryWidth.

ie

    if (xScale.ticks.length !== me.chart.data.labels.length) {
       var perc = xScale.ticks.length / me.chart.data.labels.length;
       fullBarWidth = fullBarWidth * perc;
       categoryWidth = categoryWidth * perc;
    }