Update ucam_webauth.php to work with PHP >= 7.4.

See merge request !10

Fix constructor deprecation warning. Closes #7 

Constructors should now (since PHP 5) be 'function __construct(...)', not
'function <class_name>(...)'

Add minimal test case and Travis-CI integration

The test case just tests that an object can be created.
This at least proves that the code compiles but little more.
It is however a place to start fr more extensive testing.

Tidy for publication

Remove 7th parameter to gmmktime. Fixes #3 

This parameter does nothing, has been deprecated for some
while and was removed in PHP 7.

Fix a path traversal vulnerability (reported by  Graham Rymer
<gr348@cam.ac.uk>, Sun, 08 Mar 2015 15:03:09 +0000

Additioanlly, update CHANGES file to alos include an earlier,
ureleases unversioned change and a note about some (future) version
numbers being reserved.

Add a README.md to contain most of the information previously only
available on the Wiki page pointing to this distribution.

This is actually a batch of changes by John Sutton [DAMTP], which he
describes as "enhancements and bug-fixes". The largest change he
describes thus:

"The main function authenticate($authassertionid = NULL, $testauthonly
= NULL) now takes the two arguments:

$authassertionid - is used to force re-authentication.  If specified,
it can be read as “authenticate(‘but this ticket will not do’)”.  I
use it to implement an idle timeout as follows: on every successful
authentication, retrieve the current ticket id using the id() function
and store it somewhere.  When you want to force re-authentication,
pass this ticket id back in as the first argument to authenticate().

$testauthonly - a boolean which if set true means to only test the
authentication state, i.e., return true or false accordingly but do
NOT send any headers.  This is useful when you are working with ajax
requests."