remove duplicate word from README.
Added link to Grails Turbolinks Plugin
Guard against enabling the progress bar in unsupported browsers

Fix #429
Fix #426
Merge pull request #431 from javan/fix-progress-bar-when-unsupported

Guard against enabling the progress bar in unsupported browsers
Bump version and catchup the CHANGELOG
Merge pull request #421 from yellowsnow/patch-1

Added link to Grails Turbolinks Plugin
Merge pull request #420 from jtperreault/master

remove duplicate word from README.
merge upstream
merge upstream