issue 926 dragZoom 'use strict'

-forcing 'use strict' around the whole library - removed replace calls in dragZoom directive (not in angular 1.3+   replace has been deprecated)
#926

@gitnik 
@cthrax 
@zacronos 
@kandizzy 
@tcskrovseth 
Please review

After merge I will have to bump to 2.0.11 since 2.0.10 is broken in use strict currently.
this is why travis is failing, removing now