Bugfix : respect the name order of the scripts found

Today, if we have

src/test/casperjs/
                          +- 01_firstScriptToRun.coffee
                          +- 02_secondScriptToRun.coffee

nothing guarantees the expected order of execution, ie 01_first then 02_second.

As order can matter, the plugin will reorder the scripts found to be executed, following their names.