0.15.0 (03-09-2016)

Add context store
KEMAL_ENV respects to Kemal.config.env and needs to be explicitly set.
Kemal::InitHandler is introduced. Adds initial configuration, headers like X-Powered-By.
Add send_file to helpers.
Add mime types.
Fix parsing JSON params when "charset" is present in "Content-Type" header.
Use http-only cookie for session
Inject STDOUT by default in CommonLogHandler