README.md: More info on running tests, removed link to roadmap.

The link to https://github.com/etetoolkit/ete/wiki/ROADMAP is kind of
obsolete.

I have also updated that wiki page to better reflect some of the
things that we have done for ete4.

Author: jordibc

README.md

@@ -170,12 +170,13 @@ You can launch some tests by running:
 ./run_tests.py
 ```
 
+To see all the available options for running the tests, use:
 
-# Contributing and bug reporting
-
-https://github.com/etetoolkit/ete/wiki/Contributing
+```sh
+./run_tests.py -h
+```
 
 
-# Roadmap
+# Contributing and bug reporting
 
-https://github.com/etetoolkit/ete/wiki/ROADMAP
+https://github.com/etetoolkit/ete/wiki/Contributing