README.md: Add Code Climate badge

[ci skip]
tests: Add LintTest to check syntax of PHP files
result.php: Wording changes
result.php: Allow saving if the result is different from the source
result.php: Display a note when noaccessdate is set
wikitoolbox.js: Use the default server only when rlServer is undefined
wikitoolbox.js: Update /*global*/ for JSLint
Remove php-diff in favour of wDiff
result.js: Update CSS class names for the colour legend