Fixes output in transition mixing when giving parameters in any order

In the issue #1550 it was reported that the transition mixing did not handle the parameters right when they were not provided in the following order:

```scss
@include transition([<property> <duration> <timing-function> <delay>]);
```
In order to have the same behavior as the definition of the transition rule by the W3C we should be able to accept the parameters in any order but it is important to remember that *"the first value that can be parsed as a time is assigned to the transition-duration, and the second value that can be parsed as a time is assigned to transition-delay."*

Reference:
[W3C transitions definition](http://www.w3.org/TR/css3-transitions/#transition-shorthand-property)