Increase Unicorn memory limits to 300-350

Using this limit on GitLab.com it appears we're able to reduce response
timings by about 620 milliseconds compared to the previous limit.

See gitlab-org/gitlab-ce!2421 for more information.

config.ru

@@ -7,8 +7,8 @@ if defined?(Unicorn)
     # Unicorn self-process killer
     require 'unicorn/worker_killer'
-    min = (ENV['GITLAB_UNICORN_MEMORY_MIN'] || 200 * 1 << 20).to_i
-    max = (ENV['GITLAB_UNICORN_MEMORY_MAX'] || 250 * 1 << 20).to_i
+    min = (ENV['GITLAB_UNICORN_MEMORY_MIN'] || 300 * 1 << 20).to_i
+    max = (ENV['GITLAB_UNICORN_MEMORY_MAX'] || 350 * 1 << 20).to_i
     # Max memory size (RSS) per worker
     use Unicorn::WorkerKiller::Oom, min, max