The default compiler flags in voro++'s config.mk file do not include
-fPIC, which makes it incompatible with building the shared object for
the python wrapper.

remove attempts to use urllib and use curl for all downloading. restore printing help with no flags.

- remove cross compiler stuff
- make use of Install.py consistent
- provide options for Makefile.serial and Makefile.mpi that match those in src

- build into local directory to replace existing installation is now default
- add wrapper function that calls curl in case python package has not ssl support
- have to specify -n flag to avoid wiping out the existing installation
- can specify -p to point to an existing kim-api installation (implies -n)