Normalize the Reference status when set.

Author: hainesr

lib/cff/reference.rb

@@ -393,6 +393,7 @@ def format=(fmt)
     # Sets the status of this Reference. The status is restricted to a
     # [defined set of status types](https://citation-file-format.github.io/1.0.3/specifications/#/status-strings).
     def status=(status)
+      status.downcase!
       @fields['status'] = status if REFERENCE_STATUS_TYPES.include?(status)
     end
 

test/cff_reference_test.rb

@@ -83,6 +83,9 @@ def test_status_restricted_to_allowed_types
     @reference.status = "published"
     refute_equal @reference.status, "published"
     assert_equal @reference.status, "in-press"
+
+    @reference.status = "Pre-Print"
+    assert_equal @reference.status, "pre-print"
   end
 
   def test_languages_methods