add embedded bibtex tag

fix #57

lib/jekyll/scholar/tags/bibtex.rb

+module Jekyll
+  class Scholar
+
+    class BibTeXTag < Liquid::Block
+      include Scholar::Utilities
+
+      def initialize(tag_name, arguments, tokens)
+        super
+
+        @config = Scholar.defaults.dup
+        @keys, arguments = split_arguments arguments
+
+        optparse(arguments)
+      end
+
+      def render(context)
+        set_context_to context
+        
+        BibTeX.parse(super, bibtex_options).map { |entry|
+          reference_tag entry
+
+        }.join("\n")
+      end
+    end
+
+  end
+end
+
+Liquid::Template.register_tag('bibtex', Jekyll::Scholar::BibTeXTag)
+