v1.0.0

ArgTools v1.0.0

Initial ArgTools release.

Merged pull requests:

• add support for command & pipeline arguments (#1) (@StefanKarpinski)
• tests: exercise arg_writers(path) method (#2) (@StefanKarpinski)
• tests: cover error handling code paths (#3) (@StefanKarpinski)
• README: some tweaks and improvements (#4) (@StefanKarpinski)
• tests: avoid relying on temp_cleanup_purge (#5) (@StefanKarpinski)