Fix gh-pages-from-travis Makefile target
Fix gh-pages-from-travis Makefile target

12558b9 introduced a regression where `$(GIT_BRANCH)` is used instead of `master` in the `gh-pages-from-travis` target.

kalbermattenm/ngeo,ger-benjamin/ngeo,camptocamp/ngeo,Jenselme/ngeo,Jenselme/ngeo,adube/ngeo,camptocamp/ngeo,ger-benjamin/ngeo,pgiraud/ngeo,ger-benjamin/ngeo,adube/ngeo,camptocamp/ngeo,Jenselme/ngeo,pgiraud/ngeo,pgiraud/ngeo,adube/ngeo,mygu/ngeo,kalbermattenm/ngeo,mygu/ngeo,adube/ngeo,Jenselme/ngeo,kalbermattenm/ngeo,mygu/ngeo,camptocamp/ngeo,camptocamp/ngeo