* HelpWriter.cs fixed default config file name: GitVersion.yaml -> GitVersion.yml

Author: sergiorykov

src/GitVersionExe/HelpWriter.cs

@@ -24,7 +24,7 @@ path            The directory containing .git. If not defined current directory
     /showvariable   Used in conjuntion with /output json, will output just a particular variable. 
                     eg /output json /showvariable SemVer - will output `1.2.3+beta.4`
     /l              Path to logfile.
-    /showconfig     Outputs the effective GitVersion config (defaults + custom from GitVersion.yaml) in yaml format
+    /showconfig     Outputs the effective GitVersion config (defaults + custom from GitVersion.yml) in yaml format
     /overrideconfig Overrides GitVersion config values inline (semicolon-separated key value pairs e.g. /overrideconfig:tag-prefix=Foo)
                     Currently supported config overrides: tag-prefix