added better back request method

[josephmancuso]

This PR adds a better back method than previous. You can use this like so:

a lot of the time we might have a route like this:

ROUTES = [
    get('/dashboard/create', 'Controller@show'),
    post('/dashboard/create', 'Controller@store')

]

meaning we have a GET route that shows the create form and then a POST method on the same route. In this instance we can just do this:

def store(self):
    request().back()

Which returns the current URL as the redirection but it will be the GET version of it.

---

We can also specify more explicitly what the redirection will be by using a view helper function:

<form action="{{ route('dashboard.create')" method="POST">
    {{ csrf_field|safe }}
    {{ back('/dashboard/create')|safe }}
</form>

or possibly even:

<form action="{{ route('dashboard.create')" method="POST">
    {{ csrf_field|safe }}
    {{ back(request().path)|safe }}
</form>

and then the back method will look for this new input:

def store(self):
    request().back() # returns the __back input created from the view helper

We can also specify a default just incase one is not passed in:

def store(self):
    request().back(default='/login') # returns the __back input created from the view helper or /login if that didn't exist.

[coveralls]

Coverage increased (+0.08%) to 91.359% when pulling a4f2c2d on create-better-back-method into b259858 on master.

[coveralls]

Coverage increased (+0.08%) to 91.359% when pulling a4f2c2d on create-better-back-method into b259858 on master.

[aisola]

Nice and simple. I like it.