bills:
    bill for the year (when removed from LE, should be dynamic)

    bills html, and growth types are poor code repitition / lame... could I do something more like:
        {% for gt in growth %}
            {% if gt.name == 'Min' %}
                <option value='min'
                    {% if bt.which_growth == gt.name %}selected{% endif %}
                >{{'%.2f'|format(bt.ann_growth_min)}}% {{gt.name}}</option>

CALC:
    * if I quit at different times of the financial year, technically the amount I earn will be taxed
    differently, but hard to calc - slides around with tax brackets in future

    * still get double health insurance bills sometimes (just viewing a new date might trigger this??? or at least when I changed years)

UI:
    allow shift-scrollwheel to zoom