Use root README in nuget

Author: Charles-Gagnon

src/Microsoft.Azure.WebJobs.Extensions.Sql.csproj

@@ -48,7 +48,7 @@
     </Reference>
     <None Include="pkgicon.png" Pack="true" PackagePath="" />
     <None Include="..\lib\Microsoft.SqlServer.TransactSql.ScriptDom.dll" Pack="true" PackagePath="lib/$(TargetFramework)" />
-    <None Include=".\README.md" Pack="true" PackagePath="" />
+    <None Include="..\README.md" Pack="true" PackagePath="" />
   </ItemGroup>
 
 </Project>