Sri Lankan flag fix - issue #29

Fixed an issue with Sri Lankan flag.

Issue logged:
https://github.com/lipis/flag-icon-css/issues/29

Current:
http://lipis.github.io/flag-icon-css/flags/4x3/lk.svg
![Current Sri Lankan flag](http://lipis.github.io/flag-icon-css/flags/4x3/lk.svg)


Expected:
http://upload.wikimedia.org/wikipedia/commons/1/11/Flag_of_Sri_Lanka.svg
![Current Sri Lankan flag](http://upload.wikimedia.org/wikipedia/commons/1/11/Flag_of_Sri_Lanka.svg)