Revert "Revert "V6.1.5.1""

This reverts commit 8e7336fac3a082dc55205856d5d83a7f782e63c4.
Revert "version 6.1.6"

This reverts commit 40d24246da412c77b8d533d975ef29290f2d889b.
Revert "version 6.1.5"

This reverts commit d04ab957b959824033d94245692bf12851aeaca4.

Conflicts:
	intros/intro_index.html