Fix logging for older versions of IE where console.log is a host object

The problem occurs because console.log is a host object where the type
is 'object' rather than 'function'. As such, Function.prototype.call
is unavailable directly on the object, but can be called directly.

This was introduced by commit 30930c41 which added support for IE10.
Merge pull request #9 from danielwhite/fix-ie8

Fix logging for older versions of IE where console.log is a host object