added readme to zlibtest

Author: cignoni

test/zlibtest/readme.md

@@ -0,0 +1,14 @@
+To compile this file
+
+    emcc zlibtest.cpp -s USE_ZLIB=1 -o test.html
+
+The first time you compile emcc should *automatically* retrieve/unpack/build the needed zlib.bc
+
+In my case it wrote something like:
+
+    MacCignoni:zlibtest cignoni$ emcc zlibtest.cpp -s USE_ZLIB=1 -o test.html
+    WARNING:root:retrieving port: zlib from https://github.com/emscripten-ports/zlib/archive/version_1.zip
+    WARNING:root:unpacking port: zlib
+    WARNING:root:generating port: zlib.bc...
+    WARNING:root:                           ok
+