Updated to use BeginExecuteReader instead of ReadAsync

[tomhallam]

ReadAsync doesn't work on Mono, so I updated it to use the BeginExecuteReader natively.

[gaelazzo]

I'm using var reader = await command.ExecuteReaderAsync (CommandBehavior.Default) both with mySql and SqlServer, both with Windows and Linux and it seem to work. see edge-sql and the project jsMySqlDriver for mySql driver and the project jsSqlServerDriver for sqlServer driver

and travis result for jsMySqlDriver

[agracio]

Project moved to https://github.com/agracio/edge-sql with full support for .NET Standard