Add README section on skipping code
Add README section on skipping code

Related to #304

[skip ci]

ptashman/simplecov,QuickPay/simplecov,gerry3/simplecov,hugopeixoto/simplecov,colszowka/simplecov,playpasshq/simplecov,mallikarjunayaddala/simplecov,colszowka/simplecov,irfanah/simplecov