generateRecoveryCodes

Added generateRecoveryCodes for easy generation of recovery codes for your users to GoogleAuthenticator helper class.

Also added several cleanups and forcing PHP 5.4 from now on.

Thanks to @therealssj for the suggestion!

Use PHP7 random_int

The GoogleAuthenticator class now uses random_int for the pseudo random generation. That function is available in PHP7 and there is a polyfill (linked in the README) for previous versions. If neither is present, it will default to it's current behavior.

Thanks to @inanimatt for the suggestion.

Add some additional checks and filters for making urls

Thanks to @schinkel for the merge request on this one.

Use openssl or mt_rand for random

Previously it used "rand" for generating the pseudorandom in the googleauthenticator helper class. This has now been replaced with an implementation that will create a random either from openssl if it's present or otherwise use the mt_rand option (not as good, but better then just rand).

Issuer option for link

Will allow a display of "issuer" for software that can use it.

Function to just get the OTP uri

Merge pull request #1 from pascalockert/master

Additional method to get Key URI without Google Charts