Upgrade to v2.4.7 release version

Release v2.4.7

fix bug when calling scan_time_in_minutes serveral time resulting in casting conversion every time
allow user to set a custom regex for parsing the mzML index
update readme with instructions for testing with tox
fix bug which made pymzML crash when ms_level is 0
update sphinx dependency
the reader is now reset to the inital state after iterating all spectra
fix bugs when parsing mzML files with non numerical id