Change logging format. Closes #14

The URL logged was not clickable in certain Terminal applications.
This is why we changed from brackets "[]" to braces "()"
Merge pull request #16 from tmaier/issue-14

Change logging format. Closes #14
Update .travis.yml

test for ruby 2.1.1 added
Update README.md
Use case statement in #should_be_visited?
Assignment to local variable unnecessary in
#links_for
Remove unnecessary check if it is an URI

Kernel.URI is doing this by itself
Simplify PolipusCrawler.crawl
Simplify #url_tracker and #redis
Remove begin block from HTTP#fetch_pages
Minor changes to HTTP#fetch_pages