Resolves#1071
`prohibitedWords` config parameter is an array of words. If set and case insensitive greedy match is found anywhere in the title then that newsfeed item will not be displayed. Readme updated with instructions.
Users should be careful on the words selection as careless setting may remove many or all items from the newsfeed. Some obvious mistakes like `space, comma, dot` etc. can be prevented programatically, but I left it out of this PR
Example:
with `prohibitedWords: ['dodgers']`
Original `newsItems`:
```
0:{title: "New York City, Russia, Los Angeles Dodgers: Your Wednesday Briefing", description: "Here’s what you need to know to start your day.", pubdate: "Wed, 01 Nov 2017 09:37:36 GMT", url: "https://www.nytimes.com/2017/11/01/briefing/new-yo…ssia-los-angeles-dodgers.html?partner=rss&emc=rss", sourceTitle: "New York Times"}
1:{title: "A Mangled School Bus, Bodies Everywhere; ‘It Was Surreal’", description: "A truck ramming bicyclists. The driver emerging wi…e attack, it was as confusing as it was gruesome.", pubdate: "Wed, 01 Nov 2017 09:27:41 GMT", url: "https://www.nytimes.com/2017/10/31/nyregion/nyc-sc…r-attack-truck-witnesses.html?partner=rss&emc=rss", sourceTitle: "New York Times"}
2:{title: "Dodgers 3, Astros 1 | Series tied, 3-3: With a Rally and a Romp, Dodgers Top Astros and Force Game 7", description: "Down by a run with just four innings left in Game …nst a dominating Justin Verlander. Game 7 awaits.", pubdate: "Wed, 01 Nov 2017 07:21:07 GMT", url: "https://www.nytimes.com/2017/11/01/sports/dodgers-win-game-6.html?partner=rss&emc=rss", sourceTitle: "New York Times"}
3:{title: "José Andrés Fed Puerto Rico, and May Change How Aid Is Given", description: "The chef’s huge effort is just the latest led by c…ocally based way to feed people after a disaster.", pubdate: "Wed, 01 Nov 2017 06:40:09 GMT", url: "https://www.nytimes.com/2017/10/30/dining/jose-andres-puerto-rico.html?partner=rss&emc=rss", sourceTitle: "New York Times"}
```
Filtered `newsItems`:
```
0:{title: "A Mangled School Bus, Bodies Everywhere; ‘It Was Surreal’", description: "A truck ramming bicyclists. The driver emerging wi…e attack, it was as confusing as it was gruesome.", pubdate: "Wed, 01 Nov 2017 09:27:41 GMT", url: "https://www.nytimes.com/2017/10/31/nyregion/nyc-sc…r-attack-truck-witnesses.html?partner=rss&emc=rss", sourceTitle: "New York Times"}
1:{title: "José Andrés Fed Puerto Rico, and May Change How Aid Is Given", description: "The chef’s huge effort is just the latest led by c…ocally based way to feed people after a disaster.", pubdate: "Wed, 01 Nov 2017 06:40:09 GMT", url: "https://www.nytimes.com/2017/10/30/dining/jose
```
Scenario:
* Specify more than one calendar in `config.calendars`
* Specify a maximum number of entries in `config.maximumEntries`
Result:
The module will show as many as maximumEntries for EACH calendar
Expected:
The module shall not show more than a total of maximumEntries, regardless of how many calendars I specify
Fixes#1043
