Reads an RSS-feed, captures all the articles in the link-tags, and summarizes them in a few sentences. The summaries are then written to the respective articles description tag. This allows you to read summaries of articles directly in your RSS reader, instead of having to open the article in your browser.
To add an RSS-feed, append the name of the RSS-feed together with it's url in the URL-dictionary contained in constants.py.
For example: URLS = {'BBC': 'http://feeds.bbci.co.uk/news/world/rss.xml'}.
By default, the summary consists of 5 sentences. This can be changed in constants.py by changing the SENTENCES variable to the desired number of sentences.