Add option for setting multiple allowed origins when binding

[jonhoo]

The parameter for allowed origins could also be an array of allowed origins to allow multiple sources.

[leszekgruchala]

And there is such solution...
http://postmessage.freebaseapps.com/

{
"message": "postmessage origin mismatch",
"origin": [
"http://postmessage.freebaseapps.com",
"http://www.xyz.com"
]
}
You can set this globally. However, the origin specified in the bind method will take precedence.
pm.origin = "http://www.xyz.com";