refactor container collector into subpackage

collector/main.go

@@ -0,0 +1,23 @@
+package collector
+
+import (
+	"math"
+)
+
+type Metrics struct {
+	CPUUtil    int
+	NetTx      int64
+	NetRx      int64
+	MemLimit   int64
+	MemPercent int
+	MemUsage   int64
+}
+
+type Collector interface {
+	Stream() chan Metrics
+	Stop()
+}
+
+func round(num float64) int {
+	return int(num + math.Copysign(0.5, num))
+}