@jinpark => Search in parent directories for git repo instead of failing instantly

As [noted earlier](https://github.com/ilyakava/stefon/issues/3) stefon assumes that the current working directory is the location of the .git repository to analyze.

This PR addresses the situation where a user may be in a directory nested in the project of interest when running the command. In this case, stefon will now ascend the user's directory tree either until finding a git repo or the root directory of the system.