Print vulnerability report at the end of the run

What does this MR do?

It prints a text report of the vulnerability the tool found at the end of it's standard output

Here is an example of report:

Security vulnerabilities found :
+--------------------+--------------------+--------------------+-------------------------------------------------------------------+
|      Priority      |        Tool        |     Identifier     |                                URL                                |
+--------------------+--------------------+--------------------+-------------------------------------------------------------------+
| High               | brakeman           |                    | https://brakemanscanner.org/docs/warning_types/command_injection/ |
| Possible command injection                                                                                                       |
| In app/controllers/application_controller.rb line 5                                                                              |
+--------------------+--------------------+--------------------+-------------------------------------------------------------------+
| Unknown            | gemnasium          |                    | https://github.com/mishoo/UglifyJS2/issues/751                    |
| Backdooring via erroneous minifcation of boolean expression for uglifier                                                         |
| In Gemfile.lock                                                                                                                  |
+--------------------+--------------------+--------------------+-------------------------------------------------------------------+
| Unknown            | gemnasium          | CVE-2017-15412     | https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2017-15412     |
| Denial of Service for nokogiri                                                                                                   |
| In Gemfile.lock                                                                                                                  |
+--------------------+--------------------+--------------------+-------------------------------------------------------------------+
| Unknown            | bundler_audit      | CVE-2017-15412     | https://github.com/sparklemotion/nokogiri/issues/1714             |
| Nokogiri gem, via libxml, is affected by DoS vulnerabilities                                                                     |
| In Gemfile.lock                                                                                                                  |
+--------------------+--------------------+--------------------+-------------------------------------------------------------------+
| Unknown            | bundler_audit      | 126747             | https://github.com/mishoo/UglifyJS2/issues/751                    |
| uglifier incorrectly handles non-boolean comparisons during minification                                                         |
| In Gemfile.lock                                                                                                                  |
+--------------------+--------------------+--------------------+-------------------------------------------------------------------+
| 5 security vulnerabilities.                                                                                                      |
+--------------------+--------------------+--------------------+-------------------------------------------------------------------+

Why was this MR needed?

It's needed to offer people clicking a Github status URL a way to see the detected vulnerabilities.

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• Tests added for this feature/bug

What are the relevant issue numbers?

Closes #31