10 fix add plaso timeline script

## Make add timeline script better
The add timeline script is a hack, and will always be until we have a proper Plaso frontend. But until then let's have a script that works.
Adding argument parsing and some error handling. This fixes issue #10

Reviewer: @joachimmetz

Suggestion: if you are planning to add more of these utility script think about putting the elastic search interaction code into a common class, for now you can keep it as is.