Active tab

This pull request add the `current` class (which change the text color to blue) to the selected tab in todos and profile views.

I'm quite sure about this but I created a pull request and not pushed directly because, actually, the `todos` view has the `current` class always applied to the `active` tab. Now it'll have it only when the selected tab is `active`.

It's more intuitive and has been reported several times.

![schermata del 2013-09-05 12 38 19](https://f.cloud.github.com/assets/589911/1087426/d2fb9d0e-1617-11e3-93ed-7d48d51c792e.png)
![schermata del 2013-09-05 12 37 59](https://f.cloud.github.com/assets/589911/1087427/d84a0fd4-1617-11e3-98ef-a90b37a33651.png)

Active and completed tabs in the `todos` look the same because I have no todo.

![schermata del 2013-09-05 12 37 14](https://f.cloud.github.com/assets/589911/1087429/e13f66ca-1617-11e3-8cea-265b237824dd.png)
![schermata del 2013-09-05 12 36 56](https://f.cloud.github.com/assets/589911/1087430/e15d6d1e-1617-11e3-9214-9e273fa3ea9b.png)