Fix mojibake by using Feedzirra (deprecate FeedNormalizer)

Feedzirra is actively maintained, and solve the problem that I encountered.

refs. https://www.ruby-toolbox.com/categories/feed_parsing
Integration Array generic metohds
Run rake setup task before running test at travis-ci.org

This commit will recovers failing test below.
https://travis-ci.org/fastladder/fastladder/jobs/5550963

* `config/initializers/secret_token.rb` is ignored by `.gitignore` then not under version control
* Running test without `secret_token.rb`, an `A secret is required to generate an integrity hash for cookie session data. Use config.secret_token = "some secret phrase of at least 30 characters"in config/initializers/secret_token.rb` error occured
* After run `rake setup` task (this task creates `secret_token.rb`) all tests passed again.
* Run `rake setup` task before running test suite at travis-ci, all tests will pass.

https://travis-ci.org/fastladder/fastladder/jobs/5550963
Merge branch 'fix-signup-stories-spec-failed'
Merge branch 'master' of github.com:fastladder/fastladder
Merge pull request #38 from ykzts/integration-array-generic

Integration Array generic metohds
Merge pull request #37 from uu59/use_feedzirra

Fix mojibake by using Feedzirra (deprecate FeedNormalizer)
fix about#index and subscribe#confirm not using format

access like /about/http://example.com/index.xml
raise ActionView::MissingTemplate cause by "format: :xml"
Merge branch 'master' of github.com:fastladder/fastladder
Merge pull request #40 from onk/fix_using_format

fix about#index and subscribe#confirm not using format
Merge pull request #41 from aerith/master

Use "respond_to" method for returning status "ok" or "not_found"
Merge branch 'master' of github.com:fastladder/fastladder