Add Travis CI and LuaCheck (#2)

.luacheckrc

@@ -0,0 +1,19 @@
+unused_args = false
+allow_defined_top = true
+max_line_length = 999
+
+globals ={
+    "minetest",
+}
+
+read_globals = {
+    string = {fields = {"split", "trim"}},
+    table = {fields = {"copy", "getn"}},
+}
+
+files["init.lua"].ignore = { "modname", "tab" }
+files["mysql/mysql.lua"].ignore = { "" }
+files["mysql/mysql_h.lua"].ignore = { "" }
+files["mysql/mysql_print.lua"].ignore = { "" }
+files["mysql/mysql_test.lua"].ignore = { "" }
+                                     -- ^ Ignore everything