Added jQuery < 1.4.3 compatibility

Before 1.4.3 data() did not include HTML5 data-* attributes.
Tested with jQuery 1.4.2
Fix ios 5 detection regex
Merge pull request #153 from berikv/patch-2

Fix ios 5 detection regex
Comments and update readme.
Merge branch 'master' of https://github.com/swiftyone/jquery_lazyload into swiftyone-master
Update README.
Mention also bug #144.
Prepare for 1.9.1.
Shorten the header in minified versions.
Build minified versions.