chore: update to 2.3.0

closes #301

* remove `exclude` clause from `tsconfig.json`; it was just confusing people
* karma.config + karma-test-shim can handle multiple spec source paths (issue #294)
* cosmetic `app.component.spec.ts` changes
* cosmetic `karma.config.js` changes

The package is not listed in `package.json` and https://github.com/angular/angular.io/pull/2803 will contain instructions to add it manually.

Blocked by https://github.com/angular/angular.io/pull/2781 and Angular 2.2.0.

Bug in Jasmine v.2.5.x, reported in https://github.com/jasmine/jasmine/issues/1231

Stick with v.2.4.1 (as karma-jasmine does) until the issue is resolved
Unfortunately, there is no @types/jasmine for v.2.4 but only for v.2.5.

See #266

Using `end_of_line` causes issues on windows machines.

removed advice about requiring admin access for npm install, start - this is incorrect and bad practise.

In response to https://github.com/angular/quickstart/commit/ea70d3a88dae6d3c104bb60fe343caf037e1bb76#commitcomment-19166659