Added the "--user" and "-U" flags to search trending repos by user. This flag requires an argument. If the username is not found a KeyError is returned (this is consistent with other searches that produce no results). If the username is found then only those repos owned by that user are displayed. A test has been included to validate the search functionality.
Context Closes #57
Description
Added the "--user" and "-U" flags to search trending repos by user. This flag requires an argument. If the username is not found a KeyError is returned (this is consistent with other searches that produce no results). If the username is found then only those repos owned by that user are displayed. A test has been included to validate the search functionality.