Adding file size checking, skipping files over the configured max file size

[keithwharrison]

Added a configuration for max file size (defaults to 1GB) Skipping files (and logging info) that are over the configured max file size Solves issue #48

[richq]

Thanks! I'll take a look soon. (note to self: the travis ci failure is a false positive in this case, or might need updating in an unrelated way.)