Fix broken links

[iluwatar]

The html-proofer that is included in Travis build indicates that we have some broken links.

Running ["HtmlCheck", "ImageCheck", "ScriptCheck", "LinkCheck"] on ["./_site/"] on *.html... 
Checking 391 external links...
Ran on 133 files!
- ./_site/patterns/acyclic-visitor/index.html
  *  internally linking to ../visitor/README.md, which does not exist (line 1)
- ./_site/patterns/half-sync-half-async/index.html
  *  External link http://www.cs.wustl.edu/~schmidt/PDF/PLoP-95.pdf failed: 404 No error
- ./_site/patterns/intercepting-filter/index.html
  *  External link http://www.javagyan.com/tutorials/corej2eepatterns/presentation-tier-patterns failed: 403 No error
  *  External link https://struts.apache.org/docs/interceptors.html failed: 404 No error
htmlproofer 3.0.6 | Error:  HTML-Proofer found 4 failures!
The command "bash cibuild.sh" exited with 1.

See full log at https://travis-ci.org/iluwatar/java-design-patterns/builds/565304449

[snehalatapandit]

@iluwatar ,
Hi, can I look at this change?

[iluwatar]

Yes @snehalatapandit

[hbothra15]

Hi @iluwatar, it seems this is again failing for different link
https://travis-ci.org/iluwatar/java-design-patterns/builds/583292258
In https://github.com/iluwatar/java-design-patterns/tree/master/partial-response credit section we are providing link for Partial Response in RESTful API Design and its respective URL is no more active and gives Page Not found error, hence Automagic is also failing

Do let me know if I can take this up ?

[iluwatar]

Please go ahead @hbothra15

[hbothra15]

Done, and created a PR for the same