Upgrade to gcc/g++ 4.9 for C++11 support, compile with -O2

Fixes #1

.travis.yml

@@ -1,5 +1,16 @@
 language: node_js
 node_js:
+  - "iojs-v3"
+  - "iojs-v2"
+  - "iojs-v1"
   - "0.12"
   - "0.10"
-  - "iojs"
+addons:
+  apt:
+    sources:
+      - ubuntu-toolchain-r-test
+    packages:
+      - gcc-4.9
+      - g++-4.9
+before_install:
+  - export CC="gcc-4.9" CXX="g++-4.9"

binding.gyp

@@ -3,7 +3,7 @@
     {
       'target_name': 'bufferutil',
       'include_dirs': ["<!(node -e \"require('nan')\")"],
-      'cflags': [ '-O3' ],
+      'cflags': [ '-O2' ],
       'sources': [ 'src/bufferutil.cc' ]
     }
   ]