allow environment passed in to make_all so they can be set in run_tests.py
fixed conversion/Makefile_amrclaw_2d to point to f90 rather than .f files
Change .f to .f90 in conversion Makefiles
Merge pull request #74 from rjleveque/makefiles_f90

Makefiles in src/python/clawutil/conversion/  needed updating to some .f90 rather than .f
Merge pull request #76 from rjleveque/make_all_env

allow environment passed in to make_all
Merge branch 'master' into nohup
to include other PRs that have been merged.

* master:
  Change .f to .f90 in conversion Makefiles
  fixed conversion/Makefile_amrclaw_2d to point to f90 rather than .f files
  allow environment passed in to make_all so they can be set in run_tests.py