Major refactoring and improvements

[zrashwani]

Including:

• Applying unit test on the libarary.
• Fix depth URL problem.
• Fix non-crawlable links issue.
• Ability to set options to underlying guzzle client by injecting it to constructor or using setCrawlerOptions method.
• Ability to crawl local files by setting localFile option and by introducing FilesystemClient class.
• Ability to use custom scrap clients using setScrapClient method.
• Ability to inject PSR-3 compliant logger to log crawling activity.