LB-1958: setup coverage for mocha

Added mochacov package.
Removed travis.yml coverage and added it to grunt task travis:ci
Removed loading of grunt-karma-coveralls within grunt that is done by
load-grunt-tasks.
Merge branch 'devel' of https://github.com/nistormihai/plugin-liveblog-embed-server into devel
wip(tests: server: coverage)