Trying to fix nuget in 4.5.1

Author: merbla

src/Serilog.Sinks.Splunk/Serilog.Sinks.Splunk.nuspec

@@ -16,7 +16,9 @@
         <dependency id="Splunk.Client" version="[2.1,3]" />
       </group>
       <group targetFramework="net45">
-        <dependency id="Splunk.Logging.Common" version="[1.1,2]" /> 
+        <dependency id="Serilog" version="[1.5,2)" />
+        <dependency id="Splunk.Client" version="[2.1,3]" />
+        <dependency id="Splunk.Logging.Common" version="[1.1,2]" />
       </group>
     </dependencies>
   </metadata>