Use local_time gem for timezone replacement (#2174)

For the 'time ago' value of stream entry simple statuses and the timestamp value
of detailed statuses - output their UTC value and use the browser timezone to
convert locally.

Gemfile.lock

@@ -111,6 +111,13 @@ GEM
     cocaine (0.5.8)
       climate_control (>= 0.0.3, < 1.0)
     coderay (1.1.1)
+    coffee-rails (4.2.1)
+      coffee-script (>= 2.2.0)
+      railties (>= 4.0.0, < 5.2.x)
+    coffee-script (2.4.1)
+      coffee-script-source
+      execjs
+    coffee-script-source (1.12.2)
     colorize (0.8.1)
     concurrent-ruby (1.0.5)
     connection_pool (2.2.1)
@@ -224,6 +231,8 @@ GEM
       letter_opener (~> 1.0)
       railties (>= 3.2)
     link_header (0.0.8)
+    local_time (1.0.3)
+      coffee-rails
     lograge (0.4.1)
       actionpack (>= 4, < 5.1)
       activesupport (>= 4, < 5.1)
@@ -500,6 +509,7 @@ DEPENDENCIES
   letter_opener
   letter_opener_web
   link_header
+  local_time
   lograge
   microformats2
   nokogiri