chore(package.json): update devDependencies to stable

grunt-contrib-clean v0.5.0 -> 0.6.0
grunt-contrib-compress v0.8.0 -> 0.10.0
grunt-contrib-concat v0.4.0 -> 0.5.0
grunt-contrib-connect v0.7.1 -> 0.8.0
grunt-contrib-uglify v0.4.0 -> 0.5.1
karma-coverage v0.2.1 -> 0.2.5
semver 2.3.0 -> 3.0.1

Closes #51