Update help file for install_data() due to the usage of the conn_file argument.
Improve how the conn_file argument is handled and error checked by the function install_data() per comment by @ethanwhite on #12
Update documentation and creation of help file for fetch() by adding the quiet argument.
Improve fetch() and install_data() so that they take advantage of the retriever's --table_name argument to set the path of the install for csv files.
Document that new argument data_dir for the function install_data().