Merge pull request #3 from lazytiger/master

Remove some no use code
Merge pull request #4 from lazytiger/master

add Context.Global(), add some V8 class function
Remove Context.Global(). Engine.NewContext() add global object template argument.
update README
update README
update README and sample code
Update README.md
add data support for accessor
comment V8::CancelTerminateExecution to boost TryCatch performance