Escape Prometheus querystring (#521)

* Escape Prometheus querystring

* Fix typo

pkg/scalers/prometheus.go

@@ -6,6 +6,7 @@ import (
 	"fmt"
 	"io/ioutil"
 	"net/http"
+	url_pkg "net/url"
 	"strconv"
 	"time"
 
@@ -122,7 +123,8 @@ func (s *prometheusScaler) GetMetricSpecForScaling() []v2beta1.MetricSpec {
 
 func (s *prometheusScaler) ExecutePromQuery() (float64, error) {
 	t := time.Now().UTC().Format(time.RFC3339)
-	url := fmt.Sprintf("%s/api/v1/query?query=%s&time=%s", s.metadata.serverAddress, s.metadata.query, t)
+	query_escaped := url_pkg.QueryEscape(s.metadata.query)
+	url := fmt.Sprintf("%s/api/v1/query?query=%s&time=%s", s.metadata.serverAddress, query_escaped, t)
 	r, err := http.Get(url)
 	if err != nil {
 		return -1, err