added composer files.
updated install and execute instructions.
added vendor dir for phpunit to git ignored list.
goodbye PEAR, hello Composer.
unix hands!
reconfigured composer to install phpunit executables to bin directory.
Merge pull request #465 from stopfstedt/composer-phpunit

Composerize phpunit
Merge branch 'master' into composer-phing

Conflicts:
	.gitignore
	.travis.yml