Replace usage of SpinWait struct with simple increment operation.  SpinWait.SpinOnce() takes too much time than the original Thread.SpinWait(5).

Update moq.netcore to 4.4.0.  The old version didn't specify its dependencies for the 'dotnet' group.

Trace IOException for stream.Read(). Otherwise the IO exception would be wrapped in an AggregateException, which would not be caught by the try-catch around BeginRead() method call.

Also unwrap AggregateException in EndRead() and re-throw its inner exception.

Use Volatile wrapper.

Merge branch 'UpdateNUnitTo3' of https://github.com/RogerBestMsft/StackExchange.Redis into netcore-test

Remove usage of SslStream.IsEncrypted as it is not availalbe on dnxcore.  On Desktop it simply returns IsAuthenticated.

Handle "inf" as well as "+inf"

Redis (v2.8 and v3) returns "inf" for positive infinity values, but here a "+inf" is expected. So changed the code to work with both: "+inf" as well as "inf".
See Issue #287: https://github.com/StackExchange/StackExchange.Redis/issues/287

Add package for Timer.  Use SpinWait struct to simulate the Thread.Yield.  According to MSDN it will always yield after the initial several spins.  Simple test shows it yields after 11 spins.