Merge pull request #660 from owenc4a4/test

catch error of socket
bump version to 0.5.1-pre
Remember default isolate for ProxyResolverV8

Fix #663
bump version to 0.5.1
[README] update for 0.5.1
[WIN] Enabling Visual Styles, so that tooltips can show up. Fix #72.
Merge pull request #686 from zhchbin/issue72

[WIN] Enabling Visual Styles, so that tooltips can show up. Fix #72.