fixes #27 which needed a silence file for experiments to make it easier for those who don't need audio to generate their experiment. Now you can put "silence.mp3" in the audio file column of your csv when you generate your experiment
for issue #26 we added a code to make sure blank lines would be ignored by adding "blank.lines.skip=T"
fixes #26 which is to improve the R script

* can import any csv with extra columns
* user doesn't have to have extensions in file names, it'll add .jpg or .mp3 by default
* if the user doesn't specify any audio file, a silence will be automatically used
* if there are blank lines within the csv, the script will run anyway
Merge pull request #28 from MarquisAlx/master

fixes #27 and #26 makes the R script more robust