Bump guard from 2.14.2 to 2.15.0 (#1143) [ci skip]

Bumps [guard](https://github.com/guard/guard) from 2.14.2 to 2.15.0.
- [Release notes](https://github.com/guard/guard/releases)
- [Changelog](https://github.com/guard/guard/blob/master/CHANGELOG.md)
- [Commits](https://github.com/guard/guard/compare/v2.14.2...v2.15.0)

Signed-off-by: dependabot[bot] <support@dependabot.com>

Gemfile

@@ -104,7 +104,7 @@ group :development do
   gem "bullet", "~> 5.8"
   gem "bundler-audit", "~> 0.6"
   gem "derailed_benchmarks", "~> 1.3"
-  gem "guard", "~> 2.14", require: false
+  gem "guard", "~> 2.15", require: false
   gem "guard-livereload", "~> 2.5", require: false
   gem "guard-rspec", "~> 4.7", require: false
   gem "rb-fsevent", "~> 0.10", require: false

Gemfile.lock

@@ -469,7 +469,7 @@ GEM
       multi_json (~> 1.11)
       os (>= 0.9, < 2.0)
       signet (~> 0.7)
-    guard (2.14.2)
+    guard (2.15.0)
       formatador (>= 0.2.4)
       listen (>= 2.7, < 4.0)
       lumberjack (>= 1.0.12, < 2.0)
@@ -553,7 +553,7 @@ GEM
     loofah (2.2.3)
       crass (~> 1.0.2)
       nokogiri (>= 1.5.9)
-    lumberjack (1.0.12)
+    lumberjack (1.0.13)
     mail (2.7.0)
       mini_mime (>= 0.1.1)
     memoist (0.16.0)
@@ -838,7 +838,7 @@ GEM
       multi_json (~> 1.0)
       stripe (>= 2.0.3)
     test-prof (0.7.2)
-    thor (0.20.0)
+    thor (0.20.3)
     thread_safe (0.3.6)
     tilt (2.0.8)
     timber (2.6.2)
@@ -960,7 +960,7 @@ DEPENDENCIES
   front_matter_parser (~> 0.2)
   gibbon (~> 2.2)
   google-api-client (~> 0.24)
-  guard (~> 2.14)
+  guard (~> 2.15)
   guard-livereload (~> 2.5)
   guard-rspec (~> 4.7)
   html_truncator (~> 0.4)