Fix off-by-one error in pie chart data

A pie chart with exactly 10 contexts would show up with 9 contexts +
(other).
Fix grammar in pie chart legend
Merge pull request #174 from kytrinyx/pie-chart-bug

Fix off-by-one error in pie chart data
Add heavy-handed tests against pie chart bug
initial changes to add an option to select either context or project as grouping of todos on home or tag page

* new menu item in view menu
* js to toggle view
* store setting in cookie to keep de choice of view persistent
* refactor index and tag page of todos to look more alike
* refactor context and project partials to look more alike
do a big refactor of rendering collections of todos for home page, tag page, project page, context page
remove option to show empty containers and start fixing failing cucumber scenarios
get all scenario's running again, first pass.
rebase to master
refactor done todos view and tests
hide group by project from menu to safely merge refactorings with master
remove leftover from merge failure
Tweak pie chart data tests
Merge pull request #175 from kytrinyx/pie-chart-bug

Add heavy-handed tests against pie chart bug