Update dependencies `net-imap`, `net-smtp` and `timeout`

Gemfile.lock

@@ -447,7 +447,7 @@ GEM
       uri
     net-http-persistent (4.0.2)
       connection_pool (~> 2.2)
-    net-imap (0.4.15)
+    net-imap (0.4.19)
       date
       net-protocol
     net-ldap (0.19.0)
@@ -455,7 +455,7 @@ GEM
       net-protocol
     net-protocol (0.2.2)
       timeout
-    net-smtp (0.5.0)
+    net-smtp (0.5.1)
       net-protocol
     nio4r (2.7.3)
     nokogiri (1.16.8)
@@ -842,7 +842,7 @@ GEM
     test-prof (1.4.2)
     thor (1.3.2)
     tilt (2.4.0)
-    timeout (0.4.1)
+    timeout (0.4.3)
     tpm-key_attestation (0.12.1)
       bindata (~> 2.4)
       openssl (> 2.0)