Serialize datetime to a string when dumping JSON

Resolves #28
Merge pull request #29 from marklr/patch-1

Serialize datetime to a string when dumping JSON
fixed issue 30
Merge branch 'master' of https://github.com/NikolaiT/GoogleScraper
minor improvements
fixed among other issues (better output while scraping now) issue #34
Merging with Nikolais latest