Updated WinRT nuspec
Updated WinRT nuspec

This is primarily to resolve issue #116
Removed the SQLite.WinRT.redist dependency from the WinRT which allows the nuget package to install on VS 2013 + Update 4
Added support for portable WinRT class libraries
caseydedore/SQLite.Net-PCL,fernandovm/SQLite.Net-PCL,oysteinkrog/SQLite.Net-PCL,mattleibow/SQLite.Net-PCL,igrali/SQLite.Net-PCL,igrali/SQLite.Net-PCL,TiendaNube/SQLite.Net-PCL,kreuzhofer/SQLite.Net-PCL,molinch/SQLite.Net-PCL