User friendly feedback from tests

[slavahatnuke]

now, when test fails we see some stack trace, that is good if I want to debug.
But if I am tester ( am I in tester mode ) and don't want to know why test failed,

for ex. now when this.browser.assertElementPresent('.no-element-with-this-class').then(callback)
it returns AAAAAAaaaaaa a lot of words and lines:

... line
.. line ..

async....
...line
......................
....

look like better to have feedback as:
Element is not present: .no-element-with-this-class

maybe it should depend on --debug mode, anyway we can be more user friendly here.

[Skadabr]

make sense