added default half transparent background for sticky scroll buttons
added default half transparent background for sticky scroll buttons

dplarson/gitlabhq,jirutka/gitlabhq,dreampet/gitlab,mmkassem/gitlabhq,LUMC/gitlabhq,htve/GitlabForChinese,jirutka/gitlabhq,darkrasid/gitlabhq,LUMC/gitlabhq,LUMC/gitlabhq,dplarson/gitlabhq,dreampet/gitlab,openwide-java/gitlabhq,LUMC/gitlabhq,darkrasid/gitlabhq,dplarson/gitlabhq,iiet/iiet-git,htve/GitlabForChinese,jirutka/gitlabhq,dplarson/gitlabhq,t-zuehlsdorff/gitlabhq,axilleas/gitlabhq,iiet/iiet-git,t-zuehlsdorff/gitlabhq,dreampet/gitlab,t-zuehlsdorff/gitlabhq,mmkassem/gitlabhq,openwide-java/gitlabhq,axilleas/gitlabhq,stoplightio/gitlabhq,mmkassem/gitlabhq,darkrasid/gitlabhq,openwide-java/gitlabhq,mmkassem/gitlabhq,iiet/iiet-git,t-zuehlsdorff/gitlabhq,htve/GitlabForChinese,jirutka/gitlabhq,openwide-java/gitlabhq,dreampet/gitlab,darkrasid/gitlabhq,iiet/iiet-git,htve/GitlabForChinese,stoplightio/gitlabhq,stoplightio/gitlabhq,axilleas/gitlabhq,stoplightio/gitlabhq,axilleas/gitlabhq