Issue title: Results the same every time data is polled
 Issue body: Code keeps a cached copy of the data and doesn't re-download. This is fine when pulling data that doesn't change but if you are trying to pull the market price periodically it doesn't work.

Maybe provide a switch for deactivating the cache?
 Comments: 
 Comment 0: Create a new instance of the object when you want fresh data.
{'source': 'GithubIssues', 'repo_name_with_owner': 'JECSand/yahoofinancials', 'issue_id': 812611789, 'repo_stars': 710.0}