Fix Url API

Hi,

When I try with this last commit, API doesn't work.

```
SOAP-ERROR: Parsing WSDL: Couldn't load from 'https://api.mindbodyonline.com/0_5ClassService.asmx?wsdl' : Premature end of data in tag html line 6
```

I've just re-add the last / and it works.

++