Don't compare floating point numbers for exact equality

A couple of the tests added in #1746 compared floating point numbers for exact equality. On my browser (Chrome 33 on Mac OS X) the results aren't quite the same, e.g.:
```
Error: expected 14.849242404917495 to equal 14.849242404917458
Error: expected 4585.786437626903 to equal 4585.78643762691
```
This PR uses `roughlyEqual` to add a small tolerance to the tests.