Ulimits & typo in docker-guide.md

[flmsc]

Hi,

When setting up a test environment for TheHive today, I noticed two minor issues with docker-guide.md:

• Lines 23-26 have one extra space (the linked docker-compose.yml in TheHive is correct)
• Running ElasticSearch in production mode requires increased ulimits and vm.max_map_count.

Submitting in the hopes that this might save the next person setting up an instance 5 mins. Hope that's okay -- feel free to reject or change if this is not the right place to add the changes.

Regards

[To-om]

Thank you !