Runner: glob() fallback to array [Closes #125]

PHP manual says: "On some systems it is impossible to distinguish between empty match and an error."
Collector: throws exception on multiple start() [Closes #124]
Merge pull request #127 from milo/pull-coverage-start

Collector throws exception on multiple start()
typo
Coverage template: do not scroll on click
Coverage template: prevent division by zero
ReportGenerator: allow single file as code coverage source
Merge pull request #126 from milo/pull-glob

glob() fallback to array
Merge pull request #128 from milo/pull-tweaks

Code coverage tweaks