Update Jerboa release references

ober

8fae4cee5a1965f02b8874f04425a4a70802c3c5

diff --git a/Makefile b/Makefile
index 8a1d879..ab280c2 100644
--- a/Makefile
+++ b/Makefile
@@ -1,4 +1,4 @@
-JERBOA_VERSION ?= v0.2.3
+JERBOA_VERSION ?= v0.2.8
 JERBOA_TOOL_DIR ?= ../jerboa/dist
 ifeq ($(origin JERBUILD),undefined)
 ifneq ($(wildcard $(JERBOA_TOOL_DIR)/jerbuild),)