[MCC-115109] Request URL issue

@BPONTES, as we discussed, I changed the code which created a request url like the following.
Please review this.  @tkwan-mdsol @mdsol/hypermedia-team

```
var baseAddress = "http://mdsol.com/";
var transitionUri = "./medidations";
var httpClient = new HttpClient() { BaseAddress = new Uri(baseAddress) };
var handler = new HttpClientTransitionRequestHandler(httpClient, new HaleSerializer());
var transition = new CrichtonTransition { Uri = transitionUri };
var representor = handler.RequestTransitionAsync(transition).Result;
```

### case 1. Transition url is null.
```
var baseAddress = "http://mdsol.com/";
var transitionUri = null;
```
=> Use only httpClient.BaseAddress. (http://mdsol.com)

### case 2. Transition url is a relative uri.
```
var baseAddress = "http://mdsol.com/";
var transitionUri = "./medidations";
```
=> Combine httpClient.BaseAddress and transition.Uri (http://mdsol.com/medidations)


### case 3. Transition url is a absolute uri.
```
var baseAddress = "http://mdsol.com/";
var transitionUri = "http://google.com/search";
```
=> Use only transition.Uri (http://google.com/search)