Update lint-worthy version list (#20)

diff --git a/Makefile b/Makefile
index 4bc9a07..dfc63d9 100644
--- a/Makefile
+++ b/Makefile
@@ -7,7 +7,7 @@
 # stable release.
 GO_VERSION := $(shell go version | cut -d " " -f 3)
 GO_MINOR_VERSION := $(word 2,$(subst ., ,$(GO_VERSION)))
-LINTABLE_MINOR_VERSIONS := 6
+LINTABLE_MINOR_VERSIONS := 7 8
 ifneq ($(filter $(LINTABLE_MINOR_VERSIONS),$(GO_MINOR_VERSION)),)
 SHOULD_LINT := true
 endif