IndexOutOfRangeException changed to ArgumentOutOfRangeException
Moved p/invoke to UnsafeNativeMethods
.NET 3.5 support, FastStructure class, CircularBuffer fixes

 * Basic .NET 3.5 memory-mapped file support (about 33% slower than .NET 4 implementation for byte[] ops)
 * FastStructure class for optimized reading/writing of structures (massive speed improvement upon .NET 4 SafeBuffer for structured data)
 * Fixed some security attribute warnings
 * Fixed CircularBuffer Read/Write IntPtr and adjusted all offsets to be relative to buffer start address rather than memory-mapped view
 * Updated projects to use common settings
 * Added a couple of missing test cases
 * Now signing SharedMemory assembly
 * appveyor.yml added