Added .Net 4.5 & async/await functionality

Added a new DapperExtensions.Net45 project that works exactly like Dapper for .Net 4.5 works: links all the .Net 4.0 files in and only adds an async/await compatible set on top / beside (see the two DapperAsync*.cs files).

Internally the very same sql statement builders are used as the non-async ones use, the only really addition is the underlying usage of the corresponding Dapper QueryAsync<T>(..) methods rather than the synchronous one(s). Therefore the buffer paramater has been removed as Dapper itself does not offer it for the async QueryAsync one.


Updated Dapper Nuget Package to 1.34 (the current) one along the line because async/await support in Dapper itself has improved since the originally used 1.13 version.

I attempted to 'emulate' the existing code-style as much as I could and not change the base mechanics (particularly the factory mechanics inside the *Extensions.cs file(s)).


One last thing - I also added the 'net45' entries in the the DapperExtensions.nuspec file, the later still resides in the normal DapperExtensions directory.. but I didn't want to move it out of there (not sure if/what kind of build system you have in place that maybe uses that path etc etc).

Cheers,
-J