Upgrade System.Buffers to 4.5 (#11)

* change Azure.Core version to 1.6

* Upgrade System.Buffers to 4.5.0

Author: erich-wang

src/DataLakeStore/DataLakeStore/DataLakeStore.csproj

@@ -15,7 +15,7 @@
     <PackageReference Include="Microsoft.Azure.DataLake.Store" Version="1.2.4-alpha" />
     <PackageReference Include="Microsoft.Azure.Management.DataLake.Store" Version="2.4.2-preview" />
     <PackageReference Include="NLog" Version="4.5.0" />
-    <PackageReference Include="System.Buffers" Version="4.3.0" />
+    <PackageReference Include="System.Buffers" Version="4.5.0" />
     <PackageReference Include="System.Net.Requests" Version="4.3.0" />
   </ItemGroup>