Add initial project setup with grunt

* Project can be started with 'grunt serve' now to see later how the
  timer pies look like.

* Add initial sass modules for styling of timer pies. Working with
  'grunt serve' allows live reloading of sass and html files.
Add styling for right half of timer pie

* It can be displayed now minutes from 1 to 30.

* Add reset sass module and set box-sizing to ensure that timer pies
  are displayed correctly.
Include bourbon to use its prefixing features

* Using mixins of bourbon has the advantage that the compiled css
  contains already prefixed properties, e.g. for 'border-radius' property.