[coverage-html] Add code coverage report link to readme.
[coverage-html] Add code coverage report link to readme.

kenichiii/phpseclib,phpseclib/phpseclib-php5,melya/phpseclib,thaigialai1987/phpseclib,melya/phpseclib,metaclassing/phpseclib,creatuity/phpseclib,phpseclib/phpseclib,phpseclib/phpseclib-php5,thaigialai1987/phpseclib,terrafrost/phpseclib,ericariyanto/phpseclib,splitice/phpseclib,ericariyanto/phpseclib,splitice/phpseclib,creatuity/phpseclib,paragonie-scott/phpseclib,danog/phpseclib,kenichiii/phpseclib,danog/phpseclib,paragonie-scott/phpseclib,metaclassing/phpseclib