Snappy support with 100.6.1 mongodump for above 4.2.0 mongo

• Mongo Consistent Backup will now use --compressor option snappy by default for version above and including 4.2.0
• using mongodump 100.6.1
• improved version comparison using looseversion library rather using tuple

Full Changelog: 1.4.2.154...1.4.2.155