Attempt to make thumb creation more tolerant to bug

[frankrousseau]

• Make thumb module more modular
• Try to build thumb only for jpg and png files
• remove file open step before thumbnail generation (useless with a create write stream)

[aenario]

why use mime & not just check file name 's extensions ?

mime does just that : https://github.com/broofa/node-mime/blob/master/mime.js#L74 https://github.com/broofa/node-mime/blob/master/types/mime.types#L1319 https://github.com/broofa/node-mime/blob/master/types/mime.types#L1324

[aenario]

lock printit version too

[frankrousseau]

mime is more expressive.

[aenario]

Ok, we can reconsider when moving this into the DS. LGTML :+1: