Update README.md

Fixed a mistyped character, link works now. Cheers.
Match the URL schemes between WP_CONTENT_URL and $src so the str_replace further down will work
Merge pull request #54 from cftp/feature/match-url-schemes

Match the URL schemes. You're a beautiful man Mr Wheatley :)
Merge pull request #52 from maiki/patch-1

Update README.md
Correct directory to place dependency of lessphp

The README instructed the user to place the lessphp code into `lessc`
directory. However, this is incorrect and should read as
"vendor/leafo/lessphp"
Merge pull request #55 from justin-lovell/readme-fix

Correct directory to place dependency of lessphp