Create hamming distance exercise

basic/hamming_distance.lua

@@ -0,0 +1,18 @@
+function hamming_distance(str1, str2)
+   -- Your solution here
+end
+
+-- Tests -----------------------------------------------------------------------
+
+package.path = package.path .. ";../luaunit/?.lua"
+local luaunit = require("luaunit")
+
+function test_distance_between_foo_and_bar_is_3()
+   luaunit.assertEquals(hamming_distance("foo", "bar"), 3)
+end
+
+function test_distance_between_bar_and_baz_is_1()
+   luaunit.assertEquals(hamming_distance("bar", "baz"), 1)
+end
+
+os.exit(luaunit.LuaUnit.run())