Add syntax for exceptions (#19)

WoofWare.Expect.Test/TestExceptionThrowing.fs

@@ -0,0 +1,14 @@
+namespace WoofWare.Expect.Test
+
+open NUnit.Framework
+open WoofWare.Expect
+
+[<TestFixture>]
+module TestExceptionThrowing =
+
+    [<Test>]
+    let ``Can throw an exception`` () =
+        expect {
+            snapshotThrows @"System.Exception: oh no"
+            return! (fun () -> failwith<int> "oh no")
+        }

WoofWare.Expect.Test/WoofWare.Expect.Test.fsproj

@@ -13,6 +13,7 @@
       <Compile Include="Assembly.fs" />
       <Compile Include="BulkUpdateExample.fs" />
       <Compile Include="SimpleTest.fs" />
+      <Compile Include="TestExceptionThrowing.fs" />
       <Compile Include="TestSurface.fs" />
       <Compile Include="TestSnapshotFinding\TestSnapshotFinding.fs" />
       <Compile Include="TestSnapshotFinding\TestUnicodeCharacters.fs" />