Assert: added nan()
Merge pull request #108 from milo/pull-nan

Assert: added nan()
PHP argument '-n' is always used
tests: PhpExecutable uses proper php.ini [Closes #109]
PhpExecutable: added hasXdebug()
CodeCoverage: Collector opens file immediately to ensure that file can be opened/created early
CodeCoverage: process only real file, skips eval()
Tester: added option --coverage
Tester: implemented generating HTML file for code coverage
removed coverage-report.php