Fix webview bug

Android WebView JellyBean -> Should not happen: no rect-based-test nodes found - Stack Overflow
http://stackoverflow.com/questions/12090899/android-webview-jellybean-should-not-happen-no-rect-based-test-nodes-found
Use SINGLE_COLUMN when nexus 7
Merge pull request #13 from fukayatsu/fix-webview-bug

Fix webview bug