nuget paths

* If you are going to put relative paths in the .nuspec file, make sure you always start from the same directory
[skip travis]

Author: McNeight

appveyor.yml

@@ -153,7 +153,7 @@ before_test:
 
 # scripts to run after tests
 after_test:
-  - cmd: nuget pack Build\ICSharpCode.SharpZipLib.nuspec -BasePath bin\Release -OutputDirectory bin\Release
+  - cmd: nuget pack Build\ICSharpCode.SharpZipLib.nuspec -BasePath Build -OutputDirectory bin\Release
 
 # to run your custom scripts instead of automatic tests
 test_script: