add simple method, class and extend class match with the purpose of highlight them
add link(highlighting) to definitions of the classes, extend class and method
change links in order to display others colors
Improved regex phpDefineExtendsName
add implements classes highlighting
change colour of use, namespace keyword
Syntax: Tweak groups for function names and class properties.

This commit tweaks the pull request by @rodrigore.
The four syntax groups that can be highlighted are:

- 'phpFunction' - the identifier following a 'function' keyword
- 'phpClass' - the identifier following a 'class' keyword
- 'phpClassExtends' - the class name following an 'extends' keyword
- 'phpClassImplements' - the class names following an 'implements'
keyword

'phpFunction' has been chosen after 'rubyFunction'.
Merge branch 'rodrigore/master'.

Closes #16, Add Syntax for Class and methods definitions, extend and implements classes (with/without comma).