Improve error message if no framework was loaded.

Running karma on windows 8 throws the following error when trying to run in browser:

IE 11.0.0 (Windows) ERROR You need to include some adapter that implements karma.start method!

Reproduce:

• clean node install on win8 (removed npmrc)
• npm install -g karma
• npm install -g karma-cli
• karma start -> does not throw error yet
• connect browser -> throws the aforementioned error
• karma run from another console -> throws again