FAKE NUnit can't find nunit-console

[simra]

Creating an issue for tracking. We have some bitrot and the Fake NUnit reference can't find the test runner. I suspect we either need to upgrade to NUnit3, or restrict the maximum NUnit version to something Fake can handle in paket.dependencies. I'll ask some questions on SO. cc @dsyme @tpetricek @forki in case you have any suggestions.

1. System.Exception: Start of process c:\GitHub\FSharp.Charting_20180310\tools\Nunit\nunit-console.exe failed. The system cannot find the file specified
   at Fake.ProcessHelper.ExecProcessWithLambdas@91-16.Invoke(String message) in C:\code\fake\src\app\FakeLib\ProcessHelper.fs:line 91
   at Fake.ProcessHelper.ExecProcessWithLambdas(FSharpFunc2 configProcessStartInfoF, TimeSpan timeOut, Boolean silent, FSharpFunc2 errorF, FSharpFunc2 messageF) in C:\code\fake\src\app\FakeLib\ProcessHelper.fs:line 91 at Fake.NUnitSequential.NUnit(FSharpFunc2 setParams, IEnumerable1 assemblies) in C:\code\fake\src\app\FakeLib\UnitTest\NUnit\Sequential.fs:line 26 at FSI_0005.Build.clo@113-10.Invoke(Unit _arg6) at Fake.TargetHelper.runSingleTarget(TargetTemplate1 target) in C:\code\fake\src\app\FakeLib\TargetHelper.fs:line 626

[simra]

Here is some info from paket.lock:
FAKE (4.61.3) - framework: net40, net45, net461
NUnit (3.7.1) - framework: net40, net45, net461
NUnit.ConsoleRunner (3.6.1) - framework: net40, net45, net461
NUnit.Runners (3.6.1) - framework: net40, net45, net461
NUnit.ConsoleRunner (>= 3.6.1) - framework: net40, net45, net461