Added config for driving record login module
Make Collection#fraction return null for undefined values

Need to make sure graphs display a no data message instead of a value of NaN
Fixed erroneous precision parameters

A precision of 0.01 means a tolerance of `Math.pow(10, -0.01) which is ~±1 so is totally unsuited for these tests since the outputs have a domain of [0, 1]

Setting precision to 5 means a tolerance of ±0.00001
Added an extra test for zero values in `MatrixCollection#fraction`
Merge pull request #369 from alphagov/feature/driving-record-login-module

Added config for driving record login module