Update readme with 1.5 instructions (#6464)
Update readme with 1.5 instructions (#6464)

* Update readme with 1.5 instructions

* Update metric collection instruction
DataDog/integrations-core,DataDog/integrations-core,DataDog/integrations-core,DataDog/integrations-core,DataDog/integrations-core,DataDog/integrations-core,DataDog/integrations-core,DataDog/integrations-core,DataDog/integrations-core,DataDog/integrations-core