Update ExampleProtoClass.fs with .proto definition as a comment

[jhugard]

As requested in #15, add a comment to ExampleProtoClass.fs which provides a sample .proto file which could have been used to generate the code in this file.

[ctaggart]

Strange that xunit failed again with:

  1) System.Exception: Process mono  /home/travis/build/ctaggart/froto/packages/xunit.runner.console/tools/xunit.console.exe "ProtoParser.Test/bin/Release/Froto.Parser.Test.dll" "Froto.Core.Test/bin/Release/Froto.Core.Test.dll" -parallel all -xml "bin/UnitTest.xml" -trait "Kind=Unit"  timed out.
  at Fake.ProcessHelper+ExecProcessWithLambdas@89-22.Invoke (System.String message) <0x41371ee0 + 0x0002f> in <filename unknown>:0 
  at Microsoft.FSharp.Core.PrintfImpl+StringPrintfEnv`1[TResult].Finalize () <0x40a47900 + 0x00039> in <filename unknown>:0 
  at Microsoft.FSharp.Core.PrintfImpl+Final2@235[TState,TResidue,TResult,A,B].Invoke (Microsoft.FSharp.Core.FSharpFunc`2 env, A a, B b) <0x40a47570 + 0x000f7> in <filename unknown>:0 
  at Microsoft.FSharp.Core.OptimizedClosures+Invoke@3266-1[T2,T3,TResult,T1].Invoke (T2 u, T3 v) <0x40a47530 + 0x00033> in <filename unknown>:0 
  at Microsoft.FSharp.Core.OptimizedClosures+Invoke@3253[T2,TResult,T1].Invoke (T2 u) <0x40a47500 + 0x00029> in <filename unknown>:0 
  at Fake.ProcessHelper+ExecProcessWithLambdas@89-24.Invoke (System.String arg20) <0x41371eb0 + 0x00021> in <filename unknown>:0 
  at Microsoft.FSharp.Core.FSharpFunc`2[T,TResult].InvokeFast[V] (Microsoft.FSharp.Core.FSharpFunc`2 func, Microsoft.FSharp.Core.T arg1, Microsoft.FSharp.Core.TResult arg2) <0x40a47370 + 0x000ad> in <filename unknown>:0 
  at Fake.ProcessHelper.ExecProcessWithLambdas (Microsoft.FSharp.Core.FSharpFunc`2 configProcessStartInfoF, TimeSpan timeOut, Boolean silent, Microsoft.FSharp.Core.FSharpFunc`2 errorF, Microsoft.FSharp.Core.FSharpFunc`2 messageF) <0x413686f0 + 0x01209> in <filename unknown>:0 
  at Fake.Testing.XUnit2.xUnit2 (Microsoft.FSharp.Core.FSharpFunc`2 setParams, IEnumerable`1 assemblies) <0x4136e410 + 0x00156> in <filename unknown>:0 
  at FSI_0005.Build+clo@50-6.Invoke (Microsoft.FSharp.Core.Unit _arg5) <0x4136de70 + 0x000ac> in <filename unknown>:0 
  at Fake.TargetHelper+targetFromTemplate@195[a].Invoke (Microsoft.FSharp.Core.Unit unitVar0) <0x413640a0 + 0x00023> in <filename unknown>:0 
  at Fake.TargetHelper.runSingleTarget (Fake.TargetTemplate`1 target) <0x4135c4d0 + 0x000e5> in <filename unknown>:0 
---------------------------------------------------------------------

[ctaggart]

And it passed when rerunning. Something is up with mono or xunit on linux on TravisCI.