add HTTP language

Useful for `curl -i` dumps. Had to add primary_extension although this
data is usually not saved in files, but shown as code blocks.

lib/linguist/languages.yml

@@ -579,6 +579,10 @@ HTML+PHP:
   extensions:
   - .phtml
 
+HTTP:
+  type: data
+  primary_extension: .http
+
 HaXe:
   type: programming
   lexer: haXe

test/test_language.rb

@@ -26,6 +26,7 @@ class TestLanguage < Test::Unit::TestCase
     assert_equal Lexer['HTML'], Language['HTML'].lexer
     assert_equal Lexer['HTML+Django/Jinja'], Language['HTML+Django'].lexer
     assert_equal Lexer['HTML+PHP'], Language['HTML+PHP'].lexer
+    assert_equal Lexer['HTTP'], Language['HTTP'].lexer
     assert_equal Lexer['JSON'], Language['JSON'].lexer
     assert_equal Lexer['Java'], Language['ChucK'].lexer
     assert_equal Lexer['Java'], Language['Java'].lexer