Permit YAML blocks to end with three dots

The YAML spec permits blocks to end with three dots (...) in addition to
three dashes (---): http://www.yaml.org/spec/1.2/spec.html#id2760395. Some
programs that work with Jekyll (e.g., Pandoc) prefer the dots to dashes. This
commit permits the YAML metadata block to end with either dots or dashes. It
includes tests.

Signed-off-by: Parker Moore <parkrmoore@gmail.com>

lib/jekyll/convertible.rb

@@ -43,7 +43,7 @@ module Jekyll
       begin
         self.content = File.read(File.join(base, name),
                                  merged_file_read_opts(opts))
-        if content =~ /\A(---\s*\n.*?\n?)^(---\s*$\n?)/m
+        if content =~ /\A(---\s*\n.*?\n?)^((---|\.\.\.)\s*$\n?)/m
           self.content = $POSTMATCH
           self.data = SafeYAML.load($1)
         end

test/source/_posts/2014-03-03-yaml-with-dots.md

@@ -0,0 +1,5 @@
+---
+title: Test Post Where YAML Ends in Dots
+...
+
+# Test

test/test_generated_site.rb

@@ -14,7 +14,7 @@ class TestGeneratedSite < Test::Unit::TestCase
     end
 
     should "ensure post count is as expected" do
-      assert_equal 39, @site.posts.size
+      assert_equal 40, @site.posts.size
     end
 
     should "insert site.posts into the index" do

test/test_post.rb

@@ -127,6 +127,18 @@ class TestPost < Test::Unit::TestCase
         end
       end
 
+      context "with three dots ending YAML header" do
+        setup do
+          @real_file = "2014-03-03-yaml-with-dots.md"
+        end
+        should "should read the YAML header" do
+          @post.read_yaml(@source, @real_file)
+
+          assert_equal({"title" => "Test Post Where YAML Ends in Dots"},
+                       @post.data)
+        end
+      end
+
       context "with embedded triple dash" do
         setup do
           @real_file = "2010-01-08-triple-dash.markdown"