Reporters: handle multiple runs mode
First stab at multiple runs
Use async module
Add --runs option

* use async.series
* prepare reporters to handle single / multiple runs mode
Check handling of multiple runs results
json: handle results from multiple runs
Add dependency on ascii-table
plain: handle results from multiple runs

Print out a nice table
reporter: check handling of multiple runs results only when needed
Remove run-multiple helper script
Update README
Merge pull request #251 from macbre/multiple-runs

Add --runs option to phantomas