add `bootstrap-timepicker-rails` gem
add bootstrap-timepicker-rails needs js and css require code
used bootstrap-timepicker to show time
add some test code with verify the modified
add not_found_in_database in translation
add simple content to welcome mail
Merge caok:devise_zh_absence, refs #288
add english and plaintext version
delete four parameter in class CompoundDatetime, because they are no used
tweak datapicker and timepicker config
tweak datapicker and timepicker style for small screens
Merge branch 'used_bootstrap_timepicker_rails'

fixed #274, closes #283

Conflicts:
	Gemfile
allow leave time blank, refs #274
Merge pull request #289 from windduke/issue/285-add-simple-content-to-welcome-mail

issue/285: add simple content to welcome mail