Use the same jshintrc as Leaflet

Use the same jshintrc as Leaflet, and fix all errors.
Update LICENSE

Add myself to copyright notice and add a license field to package.json.
Add jshint task to grunt

Add grunt-contrib-jshint task to grunt and add it to the default task.
Update README.md

Update README.md
Remove all submodule usage

Use node packages instead of git submodules for the developer
dependencies.
This means using the Leaflet npm module and not using leaflet-tilejson
anymore.
This patch, by incident, also fixes all examples to explicitly load the
zoomslider since it doesn't load automatically anymore since 0.6.2.
Remove old dependencies

Remove jake (since we use grunt now) and uglify-js (since we don't use
that at all).
Fix tests

Commit 165d334 made the zoom control not load automatically
anymore. This commit updates the tests accordingly.
Move to the grunt-karma task

Use the grunt karma task instead of our own hand rolled one.
Update Leaflet dependency

Update Leaflet to 0.7.1
Make example test2 work in old IE

Make a conditional check for console.log in test2.html
Update styles for 0.7.1

Leaflet 0.7.x doesn't use specific styles for IE anymore and also drops
support for IE6. This commits does the same for us.
Bump version

Bump version to 0.7.0
Merge pull request #59 from kartena/wip/0.7

Updates for 0.7 release