Add first pass attempt at adding remote URL to -c

If the -c argument is given an HTTP or FTP URL then the file will be
downloaded, extracted if neccessary, and the new path returned to
ensure that the TEMP_CONFIG_DIR has a sane location.
Return properly from __check_config_dir error case
Add https support
Add error for TEMP_CONFIG_DIR = null.

This indicates an unsupported URI scheme error in __check_config_dir
Support curl, wget or fetch for pulling down config.
Merge pull request #132 from geoffgarside/remote-config-dir

Support for passing an HTTP or FTP URL for TEMP_CONFIG_DIR