Bumped rails to version 4.2.7.1 in order to satisfy bundle-audit.

[rbclark]

From bundle-audit:

Name: actionview
Version: 4.2.5.2
Advisory: CVE-2016-6316
Criticality: Unknown
URL: https://groups.google.com/forum/#!topic/rubyonrails-security/I-VWr034ouk
Title: Possible XSS Vulnerability in Action View
Solution: upgrade to ~> 3.2.22.3, ~> 4.2.7.1, >= 5.0.0.1
Name: activerecord
Version: 4.2.5.2
Advisory: CVE-2016-6317
Criticality: Unknown
URL: https://groups.google.com/forum/#!topic/rubyonrails-security/rgO20zYW33s
Title: Unsafe Query Generation Risk in Active Record
Solution: upgrade to ~> 4.2.7.1
Vulnerabilities found!