Add analyzers for strict behavior mode

[rjmurillo]

Given

public class TestClass
{
  public virtual Task TaskAsync() => Task.CompletedTask;
}

Two cases:

1. Mock has no setup corresponding to the specified invocation
   When new Mock<TestClass>(MockBehavior.Strict).Object.TaskAsync(); executes it will throw an exception at runtime because MockBehavior.Strict is set but there is no Setup for the method TaskAsync
2. Mock has no setup that provides a return value for the specified invocation
   Similar to the first case, if the setup does not include a return, there will be a runtime exception

Related to #78

[rjmurillo]

See discussion at devlooped/moq#1520