fix (config) properly pass the config object on to the adapters

This enables configuration of adapters via grunt-karma, command-line use, etc.
For example this enables passing a "grep" option through to the mocha adapter.

Previously the options were getting lost (all except karma-specific options) in parseConfig(). Also, the config options were never being passed on correctly to the adapters, just an empty object.

Combined with https://github.com/karma-runner/karma-mocha/pull/7 closes https://github.com/karma-runner/karma-mocha/issues/6