Twitterscraper

Fixed
- Fixed --lang functionality by passing the lang parameter from its CL argument form to the generater url.

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Added
- Added "-bd / --begindate" command line arguments to set the begin date of the query
- Added "-ed / --enddate" command line arguments to set the end date of the query.
- Added "-p / --poolsize" command line arguments which can change the number of parallel processes.
Default number of parallel processes is set to 20.

Improved
- Outputfile is only created if tweets are actually retrieved.

Removed
- The ´query_all_tweets' method in the Query module is removed. Since twitterscraper is starting parallel processes by default,
this method is no longer necessary.

Changed
- The 'query_tweets' method now takes as arguments query, limit, begindate, enddate, poolsize.
- The 'query_tweets_once' no longer has the argument 'num_tweets'
- The default value of the 'retry' argument of the 'query_single_page' method has been increased from 3 to 10.
- The ´query_tweets_once' method does not log to screen at every single scrape, but at the end of a batch.

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Added
-PR 61: Adding --lang functionality which can retrieve tweets written in a specific language.
-PR 62: Tweet class now also contains the tweet url. This closes https://github.com/taspinar/twitterscraper/issues/59

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Improved
-PR 55: Adding --dump functionality which dumps the scraped tweets to screen, instead of an outputfile.

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Improved
-PR 49: scraping of replies, retweets and likes is improved.

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Added
- Tweet class now also includes 'replies', 'retweets' and 'likes'