Microsoft.IO.RecyclableMemoryStream version 1.2

Changes:

• Bugs fixed when allocating very large streams.
• Concurrent methods for reading from a single stream added.
• Support for .NET 4.0 (without ETW instrumentation).
• It is now safe to call Dispose from multiple threads on the same object.

Microsoft.IO.RecyclableMemoryStream version 1.1

Changes:

• Binaries on nuget.org are now signed through Microsoft.
• Some documentation enhancements and typo-cleanup.
• Some minor performance improvements.
• Fix behavior of Dispose() to be safe on double-dispose.