Replace functions not available in IE8

Make sure errors caught at window.onerror goes to kadira
Merge pull request #54 from mnmtanish/ie8-error-tracking

Replace functions not available in IE8
makesure Kadira.option always has an object
Kadira.option may get undefined if Kadira.connect has not been invoked
Merge branch 'error-tracking' of github.com:meteorhacks/kadira into error-tracking