implements an evented file update checker [Puneet Agarwal]

This is the implementation of the file update checker written
by Puneet Agarwal for GSoC 2015 (except for the tiny version
of the listen gem, which was 3.0.2 in the original patch).

Puneet's branch became too out of sync with upstream. This is
the final work in one single clean commit.

Credit goes in the first line using a convention understood
by the contrib app.

1 files changed, 1 insertions, 0 deletions

diff --git a/Gemfile b/Gemfile
index 260604f570..bc14498372 100644
--- a/Gemfile
+++ b/Gemfile
@@ -45,6 +45,7 @@ end
 
 # Active Support.
 gem 'dalli', '>= 2.2.1'
+gem 'listen', '~> 3.0.3'
 
 # Active Job.
 group :job do