Merge branch 'release/0.6.1'
Merge branch 'release/0.6.2'
Merge branch 'release/0.6.3'
Add the MONGODB_STOP_ON_DUPLICATE option.

 - It allows to close a scrapy spider when a certain amount of duplicate insertion in mongodb is reached.
Bump to version 0.6.4
Merge branch 'ivanfrain-master' into develop