Add HaveLocation, NotHaveLocation and Be308PermanentRedirect assertions

[adrianiftode]

HaveLocation assertions

 [Fact]
 public async Task Post_ReturnsCreatedAndWithContent()
 {
     // Arrange
     var client = _factory.CreateClient();

     // Act
     var response = await client.PostAsync("/api/comments", new StringContent(/*lang=json,strict*/ @"{
               ""author"": ""John"",
               ""content"": ""Hey, you...""
             }", Encoding.UTF8, "application/json"));

     // Assert
     response.Should().Be201Created()
         .And.HaveLocation().And.BeValue("http://localhost/api/Comments/1")
         .And.BeAs(new
     {
         Author = "John",
         Content = "Hey, you..."
     });
 }

NotHaveLocation assertions

        [Fact]
        public async Task Post_WithNoAuthorButWithContent_Returns_Bad_Request_With_No_Location()
        {
            // Arrange
            var client = _factory.CreateClient();

            // Act
            var response = await client.PostAsync("/api/comments", new StringContent(/*lang=json,strict*/ @"{
                                          ""content"": ""Hey, you...""
                                        }", Encoding.UTF8, "application/json"));

            // Assert
            response.Should().Be400BadRequest()
                .And.NotHaveLocation("Bad Request responses are not designed to have Location headers.");
        }

Addresses issue #58