Clarify the meaning of the ‘payas’ prefix used in the Elisp code

The source of the abbreviation may not be obvious to other
developers, so it deserves a small mention.  This patch also helps
make it clear that any function with the ‘payas’ prefix is internal to
the Elisp package and no developer should rely on those functions
outside of ‘php-auto-yasnippets.el’ file itself.
Mention that the package uses the Semantic Versioning scheme
Use a method class name in the ‘group’ if there is no extension

The commentary in the PHP program says that it uses the class name for
a method to create the ‘group’ directive even in the absence of an
available extension name.  But the code logic does not match the
explanation in the comments.  This patch changes the code so that it
has the behavior that the commentary describes.
Create sub-groups for methods with a class belonging to a namespace

It is possible that

    $function->getDeclaringClass()->getName()

will return a class name belonging to a namespace.  If this is the
case then we can use the namespace to further organize the snippet we
create into more sub-groups.  All we need to do is replace PHP’s
namespace separator, the backslash, into YASnippet’s sub-group
separator, the period.
Update to version 0.8.0
Test the server name when running the auxiliary PHP program

It is possible for PHP_SAPI to be equal to ‘cli’ even when the program
does not run from the command-line.  A more thorough test is to also
make sure the value of $_SERVER["SERVER_NAME"] is null.