readded /dev/urandom, the primary source for safe randomness in PHP 7, random_compat and mcrypt

INSTALL.md

@@ -12,7 +12,8 @@ the options and adjust them as you see fit.
 
 - PHP version 5.3 or above
 - _one_ of the following sources of cryptographically safe randomness is required:
-  - PHP 7
+  - PHP 7 or higher
+  - open_basedir access to /dev/urandom
   - [Libsodium](https://download.libsodium.org)
   - mcrypt extension
   - com_dotnet extension