adds reference tag tests

#8

features/reference.feature

+Feature: Formatted References
+  As a scholar who likes to blog
+  I want to reference cool papers and books from my bibliography
+
+  @tags @referebce
+  Scenario: A Simple Reference
+    Given I have a scholar configuration with:
+      | key          | value             |
+      | source       | ./_bibliography   |
+      | bibliography | my_references     |
+    And I have a "_bibliography" directory
+    And I have a file "_bibliography/my_references.bib":
+      """
+      @book{ruby,
+        title     = {The Ruby Programming Language},
+        author    = {Flanagan, David and Matsumoto, Yukihiro},
+        year      = {2008},
+        publisher = {O'Reilly Media}
+      }
+      """
+    And I have a page "scholar.html":
+      """
+      ---
+      ---
+      {% reference ruby %}
+      """
+    When I run jekyll
+    Then the _site directory should exist
+    And the "_site/scholar.html" file should exist
+    And I should see "Matsumoto, Y. \(2008\). <i>The Ruby" in "_site/scholar.html"
+
+  @tags @reference
+  Scenario: Missing references
+    Given I have a scholar configuration with:
+      | key          | value             |
+      | source       | ./_bibliography   |
+      | bibliography | my_references     |
+    And I have a "_bibliography" directory
+    And I have a file "_bibliography/my_references.bib":
+      """
+      @book{ruby,
+        title     = {The Ruby Programming Language},
+        author    = {Flanagan, David and Matsumoto, Yukihiro},
+        year      = {2008},
+        publisher = {O'Reilly Media}
+      }
+      """
+    And I have a page "scholar.html":
+      """
+      ---
+      ---
+      {% reference java %}
+      """
+    When I run jekyll
+    Then the _site directory should exist
+    And the "_site/scholar.html" file should exist
+    And I should see "missing reference" in "_site/scholar.html"