Update jquery.mobile.iscrollview.js

Check for iscroll instance before call refresh
fix iscroll_init
Fix `topSpacerClass is undefined` error in `_undoAddSpacers`

Fixed a `topSpacerClass is undefined` error, that was being thrown when using the destroy method.
Updated jQuery Mobile 1.4 in demo from alpha2 to RC1
Merge remote-tracking branch 'github-VitaliiBlagodir/master'
Caught a typo in the docs
Merge remote-tracking branch 'github-sathvikp/patch-1'
Merge remote-tracking branch 'github-piscis/master'
Document pull request #80
Rev version to 1.3.4
Rev to 1.3.5, built the demo this time...