Make sure golint pass on the code base

.travis.yml

Makefile

locale/locale.go

locale/translations.go

model/theme.go

model/user.go

reader/feed/handler.go

reader/opml/handler.go

reader/processor/processor.go

reader/rewrite/rewriter.go

server/api/controller/category.go

server/api/controller/feed.go

server/api/controller/user.go

server/api/payload/payload.go

server/core/context.go

server/core/handler.go

server/middleware/basic_auth.go

server/middleware/context_keys.go

server/middleware/csrf.go

server/middleware/middleware.go