added regex parsing and modified MediaBuilder

MediaBuilder no longer requires media_type as argument. on initialization, new class function get_suggested_metadata() will run regex against the name to determine media_type. regex is not perfect, hence "suggested" metadata. this now effects collect_metadata which will now use the suggested metadata as a defaults, confirmed by stdin, unless explicitly passed media_type as argument (optional).

verify_source_data() no longer changes directory.

build_media() now takes optional media_type argument to be passed over to collect_metadata(). public mutators have been consolidated here. now, a class instance doesn't need to call collect_metadata(), verify_source_data(), format_filename(), and preexisting() before calling build_media(), because build_media() takes care of it all. also, some changes to media file path and removed change directory.