Add Block Comments as a ruby til.

ruby/block-comments.md

@@ -0,0 +1,16 @@
+# Block Comments
+
+Ruby supports (ugly) block comments. They look like this:
+
+```ruby
+=begin
+This is a block comment.
+
+I can put whatever I want in here.
+=end
+def do_something
+  ...
+end
+```
+
+[source](http://stackoverflow.com/questions/536760/block-commenting-in-ruby)