Use example files to allow proper git-ignoring

The following files:

* myhosts
* blacklist
* whitelist

can be all be modified by the user for personal usage.
However, git is tracking these files since they exist
in the repository, which makes it difficult to do so
without accidentally pushing one's own customizations.

This commit converts those examples to ".example" files,
which serve as the defaults if one of the files listed
above does not exist.

Closes gh-144.

whitelist.example

@@ -0,0 +1,2 @@
+# Domains added below will be ignored, For example:
+# your-domain-name.com