Feature/fix #156 (#160)

* change config creator to not throw exception in there is an error......lord i hate this config creator code I need to sort it out.

* Remove method that we are not using anymore..

* throw exception and add errors to message

* train hacking and some refactoring

* bs test for code coverage

* actually return the errors in the exception

test/Ocelot.AcceptanceTests/CannotStartOcelotTests.cs

@@ -0,0 +1,58 @@
+
+using System;
+using System.Collections.Generic;
+using Microsoft.AspNetCore.Hosting;
+using Ocelot.Configuration.File;
+using Shouldly;
+using TestStack.BDDfy;
+using Xunit;
+
+namespace Ocelot.AcceptanceTests
+{
+    public class CannotStartOcelotTests : IDisposable
+    {
+        private IWebHost _builder;
+        private readonly Steps _steps;
+        private string _downstreamPath;
+
+        public CannotStartOcelotTests()
+        {
+            _steps = new Steps();
+        }
+
+        [Fact]
+        public void should_throw_exception_if_cannot_start()
+        {
+            var invalidConfig = new FileConfiguration()
+            {
+                ReRoutes = new List<FileReRoute>
+                {
+                    new FileReRoute
+                    {
+                        UpstreamPathTemplate = "api",
+                        DownstreamPathTemplate = "test"
+                    }
+                }
+            };
+
+            Exception exception = null;
+            _steps.GivenThereIsAConfiguration(invalidConfig);
+            try
+            {
+                _steps.GivenOcelotIsRunning();
+            }
+            catch(Exception ex)
+            {
+                exception = ex;
+            }
+
+            exception.ShouldNotBeNull();
+        }
+        
+        public void Dispose()
+        {
+            _builder?.Dispose();
+            _steps.Dispose();
+        }
+    }
+}