Travis: use Lua from lua.org again (#1244)

This reverts commit cf96296f27 (partly).

Fixes https://github.com/awesomeWM/awesome/issues/1242.
Ref: https://github.com/awesomeWM/awesome/pull/1243#issuecomment-264212802.

.travis.yml

@@ -51,7 +51,7 @@ install:
   - |
     set -ev
     if [[ "$LUA" == "5.3" ]]; then
-      wget https://github.com/lua/lua/releases/download/5.3.3/lua-5.3.3.tar.gz -O lua.tar.gz
+      wget http://www.lua.org/ftp/lua-5.3.3.tar.gz -O lua.tar.gz
       tar -xvzf lua.tar.gz
       (cd lua-5.3.3/src \
         && make SYSCFLAGS="-DLUA_USE_LINUX -ULUA_COMPAT_5_2 -DLUA_USE_APICHECK" SYSLIBS="-Wl,-E -ldl -lreadline" LUA_A=liblua.so MYCFLAGS="-fPIC" RANLIB=: AR="gcc -shared -ldl -o" liblua.so \