Yet another try of updating the git requirements.

Author: sv2518

requirements-git.txt

@@ -1,4 +1,4 @@
 git+https://github.com/firedrakeproject/petsc.git@firedrake#egg=petsc
 --no-deps git+https://github.com/firedrakeproject/petsc4py.git@firedrake#egg=petsc4py
 git+https://github.com/coneoproject/COFFEE.git#egg=coffee
---recurse-submodules git+https://github.com/firedrakeproject/loopy.git@cvec#egg=loopy
+-r git+https://github.com/firedrakeproject/loopy.git@cvec#egg=loopy