fix(adapter): cleanup error stack trace

# Proposal for #60

Replaces the following:

```Bash
Chrome 40.0.2214 (Mac OS X 10.9.5) xxx should return false 1 FAILED
	Expected true to be false.
	Error: Expected true to be false.
        at stack (/foo/bar/node_modules/jasmine-core/lib/jasmine-core/jasmine.js:1441:17)
        at buildExpectationResult (/foo/bar/node_modules/jasmine-core/lib/jasmine-core/jasmine.js:1411:14)
        at Spec.Env.expectationResultFactory (/foo/bar/node_modules/jasmine-core/lib/jasmine-core/jasmine.js:533:18)
        at Spec.addExpectationResult (/foo/bar/node_modules/jasmine-core/lib/jasmine-core/jasmine.js:293:34)
        at Expectation.addExpectationResult (/foo/bar/node_modules/jasmine-core/lib/jasmine-core/jasmine.js:477:21)
        at Expectation.toBe (/foo/bar/node_modules/jasmine-core/lib/jasmine-core/jasmine.js:1365:12)
        at /foo/bar/baz.spec.js:23:29
        at /foo/bar/baz.js:18:20
```

with a concise and useful:

```Bash
Chrome 40.0.2214 (Mac OS X 10.9.5) xxx should return false 1 FAILED
	Expected true to be false.
        at /foo/bar/baz.spec.js:23:29
        at /foo/bar/baz.js:18:20
```

Also handles multiline error message in PhantomJS:

```Bash
PhantomJS 1.9.8 (Mac OS X) xxx should return false 1 FAILED
	TypeError: 'undefined' is not a function (evaluating 'zzz(function (res) {
	                expect(res).toBe(false);
	                done();
	            })')
	    at /foo/bar/baz.spec.js:31
```

Note that karma specifics, such as:

```Bash
	    ...
	    at http://localhost:7018/karma.js:185
	    at http://localhost:7018/context.html:1229
```

have been removed. Maybe we should keep context.html? Thoughts?
By the way I'm aware that there is an `indexOf` function (not on prototype) in the adapter.js and even tests for it. However, it is never actually used! So, unless a shim is introduced somehow, the code should have been failing on IE below 9 even before this PR.

Now, if we really want to resurrect the dinosaurs, I would recommend opening another issue specifically for this case.