increase version number

Author: Knagis

CommonMark.NET.nuspec

@@ -2,7 +2,7 @@
 <package xmlns="http://schemas.microsoft.com/packaging/2011/10/nuspec.xsd">
   <metadata>
     <id>CommonMark.NET</id>
-    <version>0.15.0</version>
+    <version>0.15.1</version>
     <title>CommonMark.NET</title>
     <authors>Kārlis Gaņģis</authors>
     <licenseUrl>https://raw.githubusercontent.com/Knagis/CommonMark.NET/master/LICENSE.md</licenseUrl>