Fixed default server for local vagrant installations

Hi @teleyinex,

I have installed locally the pybossa server through vagrant and I was following up the step-by-step tutorial for the flickrperson app. 

I have tried to create the app but did not work, looking into the Exceptio I've got I realised that the default server was not defined correctly because of the ending slash.

```
python createTasks.py  -k API-KEY -s http://localhost:5000/ -c
```
Did not work, but
```
python createTasks.py -k API-KEY -s http://localhost:5000 -c
```
Did work.

So I have just removed the ending slash and the help example as well

Cheers

Juan