Add a guard against an empty message data

There was an exception thrown when a message with an empty data was sent to the document, f.e.postMessage(null, '*'). This release fixes that problem.

setImmediate was synchrounous in IE8

v0.1.6

Release v0.1.6 (One more fix for setImmediate)

Fix setImmediate for IE8-9

v0.1.5

One more bump to v0.1.5

v0.1.4

Small code improvement

v0.1.2

Better async execution

v0.1.1

Ability to specify after-call callbacks

v0.1.0

Initial release