Update change log
Add memcache CAS stats
Merge pull request #924 from DataDog/SNMP_checks

Snmp checks
Revert "Merge pull request #924 from DataDog/SNMP_checks"

This reverts commit 4361a06b64c6c888c951bc81b156a5fe37d86502, reversing
changes made to e1f4e0d0aef7854e1448c8c4847d1e3eb49f9428.
Merge pull request #982 from Shopify/add_memcache_cas_stats

Add memcache CAS stats
Update changelog
Fix tests
Only collect MySQL metrics from /proc on linux machines.

Fix #984
Merge with master