Also accept upper case in wordlist names.

There is no need for us to enforce lowercase wordlist names. It
could even confuse people.

diceware/__init__.py

@@ -152,7 +152,7 @@ def get_wordlist_path(name):
     if not RE_WORDLIST_NAME.match(name):
         raise ValueError("Not a valid wordlist name: %s" % name)
     basename = 'wordlist_%s.txt' % name
-    return os.path.join(WORDLISTS_DIR, basename.lower())
+    return os.path.join(WORDLISTS_DIR, basename)
 
 
 def insert_special_char(word, specials=SPECIAL_CHARS, rnd=None):

tests/test_diceware.py

@@ -110,12 +110,6 @@ class TestDicewareModule(object):
         assert exc_info.value.args[0].startswith(
             'Not a valid wordlist name')
 
-    def test_get_wordlist_path_loweres_country_code(self):
-        # upper case country codes are lowered
-        assert os.path.basename(get_wordlist_path('de')) == 'wordlist_de.txt'
-        assert os.path.basename(get_wordlist_path('De')) == 'wordlist_de.txt'
-        assert os.path.basename(get_wordlist_path('DE')) == 'wordlist_de.txt'
-
     def test_insert_special_char(self):
         # we can insert special chars in words.
         fake_rnd = FakeRandom()