Correctly display exception for each failed step

Related to issue #191.
There are no tests yet and code is a bit hacky in several places.

Example:
```Java
public class MultipleFailuresTest {
    @Step
    private static void stepThatCatchesException() {
        try {
            stepThatThrowsException();
        } catch (Exception ignored) {
        }
    }

    @Step
    private static void stepThatThrowsException() throws Exception {
        stepThatDoesNothing();
        throw new Exception("fail");
    }

    @Step
    private static void stepThatDoesNothing() {
    }

    @Step
    private static void stepWithFailedAssert() {
        assertThat(1, equalTo(2));
    }


    @Test
    public void testTwoExceptions() {
        stepThatCatchesException();
        stepWithFailedAssert();
    }
}
```

Before:
![selection_006](https://cloud.githubusercontent.com/assets/2046080/4023866/45f94ea6-2bab-11e4-8952-0a10a777e662.png)

After:
![selection_005](https://cloud.githubusercontent.com/assets/2046080/4023864/13780530-2bab-11e4-8825-38620e804eb4.png)


there is more simple solution. Put the following directive into `directives.js` file
```js
.directive('failureMessage', function() {
    return {
         scope: {
              failure: '=failureMessage'
         },
         templateUrl: 'templates/xUnit/failure.html'
    }
});
And move failure template to a separate file. File placement should be match with the `templateUrl` property in definition.
Then you can use the following markup to create a failure block:
```html 
<div failure-message="testcase.failure"></div>
```
or in the case of step:
```html
<div failure-message="step.failure"></div>
```