Add percentage tax charge tests from legacy calculator
Remove results box where there's no calculation
Rephrase results when nothing is owed

Adds the current net income threshold to determine how results are displayed.
Move conditional redirect to before filter
Refactor controller vars into helper methods
Fix merge with master
Update spec description
Merge pull request #10 from alphagov/fix_calculator_results

Fix calculator results
changes the width css
Merge pull request #11 from alphagov/css-width-change

changes the width css