use native Array#empty?
minor refactor of TagHelpers
do not apply default layout to templates with external engine, fixes #1727
add volatile failure for Padrino::Cache test
add POST, HEAD, PUT, DELETE tests for Padrino::Cache
refactor Padrino::Cache
get controller-wide expires to work
Do not pass :submit_options as an attribute of form element in button_to
Prepare changelog for 0.12.3
fix changes [skip ci]
only use mutex for init on java platform, fixes #1732
fix ignore newline by after textarea's opening tag
Merge pull request #1736 from krororo/fix-ignore-newline

fix textarea value with leading newline
Change email condition for default AR4.1 in minirecord
Merge pull request #1738 from tyabe/fix_admin_template

Change email condition for default AR4.1 in minirecord
allow constants in :with, allow more arguments in route verbs, ref #1733
Merge pull request #1739 from padrino/with-strings

allow constants in :with, allow more arguments in route verbs
update changelog [skip ci]
introduce starting gemified app, closes #1716
do not force logger setup