Don't consider versions with build metadata to be unstable

Our backend was behaving properly in this regard, but the front end was
considering any version that had build metadata to be unstable. There's
no reason for us to have this detection be hand-rolled, we can use a
proper semver library to determine whether something is a prerelease or
not.

Author: sgrif

app/routes/crate/version.js

@@ -1,6 +1,7 @@
 import { observer } from '@ember/object';
 import Route from '@ember/routing/route';
 import { inject as service } from '@ember/service';
+import semver from 'semver';
 
 import fetch from 'fetch';
 import ajax from 'ember-fetch/ajax';
@@ -20,27 +21,7 @@ export default Route.extend({
         const controller = this.controllerFor(this.routeName);
         const maxVersion = crate.get('max_version');
 
-        const isUnstableVersion = version => {
-            const versionLen = version.length;
-            let majorMinorPatchChars = 0;
-            let result = false;
-
-            for (let i = 0; i < versionLen; i++) {
-                const char = version.charAt(i);
-
-                if (!isNaN(parseInt(char)) || char === '.') {
-                    majorMinorPatchChars++;
-                } else {
-                    break;
-                }
-            }
-
-            if (versionLen !== majorMinorPatchChars) {
-                result = true;
-            }
-
-            return result;
-        };
+        const isUnstableVersion = version => !!semver.prerelease(version);
 
         const fetchCrateDocumentation = () => {
             if (!crate.get('documentation') || crate.get('documentation').substr(0, 16) === 'https://docs.rs/') {

ember-cli-build.js

@@ -51,6 +51,9 @@ module.exports = function(defaults) {
     app.import('node_modules/timekeeper/lib/timekeeper.js', {
         using: [{ transformation: 'cjs', as: 'timekeeper' }],
     });
+    app.import('node_modules/semver/semver.js', {
+        using: [{ transformation: 'cjs', as: 'semver' }],
+    });
 
     return app.toTree();
 };