Encode run and tag names (#480)

This change encodes the names of runs and tags included within the GET
parameters of URIs for the audio, image, and pr_curve plugins. We pass
those run and tag names into encodeURIComponent.

Fixes #477. I verified that the audio, image, and PR curve plugins WAI.

Author: chihuahua

tensorboard/plugins/audio/tf_audio_dashboard/tf-audio-loader.html

@@ -211,9 +211,9 @@
         }
         this._metadataCanceller.cancelAll();
         const router = getRouter();
-        const baseURL = router.pluginRoute("audio", "/audio");
-        const query = `run=${this.run}&tag=${this.tag}&sample=${this.sample}`;
-        const url = baseURL + (baseURL.indexOf('?') !== -1 ? '&' : '?') + query;
+        const route = router.pluginRunTagRoute("audio", "/audio")(
+            this.tag, this.run);
+        const url = `${route}&sample=${this.sample}`;
         const updateSteps = this._metadataCanceller.cancellable(result => {
           if (result.cancelled) {
             return;

tensorboard/plugins/image/tf_image_dashboard/tf-image-loader.html

@@ -306,9 +306,9 @@
         }
         this._metadataCanceller.cancelAll();
         const router = getRouter();
-        const baseURL = router.pluginRoute("images", "/images");
-        const query = `run=${this.run}&tag=${this.tag}&sample=${this.sample}`;
-        const url = baseURL + (baseURL.indexOf('?') !== -1 ? '&' : '?') + query;
+        const route = router.pluginRunTagRoute("images", "/images")(
+            this.tag, this.run);
+        const url = `${route}&sample=${this.sample}`;
         const updateSteps = this._metadataCanceller.cancellable(result => {
           if (result.cancelled) {
             return;