Adds backup color for treemaps if there are too many different categories
Adds backup color for treemaps if there are too many different categories

(closes #49)

aumayr/beancount-web,corani/beancount-web,yagebu/fava,yagebu/fava,aumayr/beancount-web,corani/beancount-web,beancount/fava,beancount/fava,aumayr/beancount-web,beancount/fava,beancount/fava,yagebu/fava,yagebu/fava,beancount/fava,corani/beancount-web,corani/beancount-web,aumayr/beancount-web,yagebu/fava