Maintenance: Bump guard from 2.17.0 to 2.18.0

Bumps [guard](https://github.com/guard/guard) from 2.17.0 to 2.18.0.
- [Release notes](https://github.com/guard/guard/releases)
- [Commits](guard/guard@v2.17.0...v2.18.0)

Gemfile.lock

@@ -248,13 +248,13 @@ GEM
       activesupport (>= 4.2.0)
     gmail_xoauth (0.4.2)
       oauth (>= 0.3.6)
-    guard (2.17.0)
+    guard (2.18.0)
       formatador (>= 0.2.4)
       listen (>= 2.7, < 4.0)
       lumberjack (>= 1.0.12, < 2.0)
       nenv (~> 0.1)
       notiffany (~> 0.0)
-      pry (>= 0.9.12)
+      pry (>= 0.13.0)
       shellany (~> 0.0)
       thor (>= 0.18.1)
     guard-compat (1.2.1)