Arborist validates the branch against the configuration setting

[Stargator]

Once #4 is finished, then we need to look for the configuration option that defines the regular expression for branch names.

This issue will:

• Pull the value of the regular expression from the variable containing the configuration options.
• If no value for that option is found, then use the default regular expression.
• If a value was found, replace the default regular expression with the expression from the config.