v1.0.0-beta.3

Changelog

1. Added support for proper error return codes. So, when a command returns an error message, the exit code is anything other than 0.
2. The database path can be specified with a new environment variable TASKCORE_DB_PATH. If you want to store the tasks and categories in a different path, you can set the environment variable to configure it so. Thanks, @navarroaxel for the contribution.
3. The total number of the active and completed task is now displayed next to their headers when requested with ls -c command.
4. The database can be wiped out with the new command clear --force to start over. Thanks, @navarroaxel for the contribution.
5. Various other fixes and improvements...