Default to storing config under user's home directory

[dchanm]

The script currently stores the configuration data in the directory from where it executes. This means that separate runs on the same machine from different directories register a different machine. We can default to $HOME and provide a fallback to the current directory if $HOME is not defined.

We will need to provide a fallback mechanism so that we don't break user's who have been running the script from the same directory. A possible workflow is

• Attempt to read config data from home directory
• Attempt to read config data from current directory
• Run script
• Save config data to home directory
• Save config data to current directory if previous step failed

This leaves old config data in the current directory, but ensures that the data is copied over.