updated nuspec for 1.8 release

Author: markheath

NAudio.nuspec

@@ -5,8 +5,8 @@
     <version>@build.number@</version>
     <authors>Mark Heath</authors>
     <owners>Mark Heath</owners>
-    <licenseUrl>http://naudio.codeplex.com/license</licenseUrl>
-    <projectUrl>http://naudio.codeplex.com/</projectUrl>
+    <licenseUrl>https://github.com/naudio/NAudio/blob/master/license.txt</licenseUrl>
+    <projectUrl>https://github.com/naudio/NAudio</projectUrl>
     <requireLicenseAcceptance>false</requireLicenseAcceptance>
     <description>NAudio, an audio library for .NET</description>
     <summary />