Merge pull request #1 from boegel/change_impi_default_compiler

fix typos
Merge pull request #2 from boegel/change_impi_default_compiler

check compiler env vars before using them
Update mpiicc etc. for consistency
Update impi.py

Added individual triggers for the environment variables and the aliases, as well as a catch-all for everything
Update impi.py

Added a debug error statement
minor style fixes