Add required test dependencies to package.json

Added required karma plugins to successfully run the tests with a fresh system (jasmine & chrome launcher plugins).
Card Indices

It is now possible to access the index of a card from within the card's template. This is accessible via the $index property of the card card reference like {{card.$index}}. This should close issue #6.

Note that this index refers to the index of the original collection and not to the (generated) column index. The existing tests are extended to cover this feature.
Update README to reflect the new $index property feature
Merge pull request #23 from sebastianoe/master

Allow to access the card index from within the card' template (#6).