BS4 now requires Popper

package-lock.json

@@ -1,6 +1,6 @@
 {
   "name": "sage",
-  "version": "9.0.0-beta.3",
+  "version": "9.0.0-beta.4",
   "lockfileVersion": 1,
   "requires": true,
   "dependencies": {
@@ -655,13 +655,9 @@
       }
     },
     "bootstrap": {
-      "version": "4.0.0-alpha.6",
-      "resolved": "https://registry.npmjs.org/bootstrap/-/bootstrap-4.0.0-alpha.6.tgz",
-      "integrity": "sha1-T1TdM6wN6sOyhAe8LffsYIhpycg=",
-      "requires": {
-        "jquery": "3.2.1",
-        "tether": "1.4.0"
-      }
+      "version": "4.0.0-beta",
+      "resolved": "https://registry.npmjs.org/bootstrap/-/bootstrap-4.0.0-beta.tgz",
+      "integrity": "sha512-I/r3fYtUZr+rUNkh8HI+twxZ56p6ehNn27eA1XSebLVQKAJ2xZHnEvZrSR+UR2A/bONcd9gHC3xatVhQlH6R6w=="
     },
     "brace-expansion": {
       "version": "1.1.8",
@@ -8402,6 +8398,11 @@
         "logalot": "2.1.0"
       }
     },
+    "popper.js": {
+      "version": "1.11.1",
+      "resolved": "https://registry.npmjs.org/popper.js/-/popper.js-1.11.1.tgz",
+      "integrity": "sha512-wwp6RVokzjO4qh86qFeTw/zEw8y0uqB1U82LWTUExBDq8EJx/8svxDXVQB2jxTjRX+J+S++tQkbWnbOuOykZFw=="
+    },
     "portscanner": {
       "version": "2.1.1",
       "resolved": "https://registry.npmjs.org/portscanner/-/portscanner-2.1.1.tgz",
@@ -12640,11 +12641,6 @@
         }
       }
     },
-    "tether": {
-      "version": "1.4.0",
-      "resolved": "https://registry.npmjs.org/tether/-/tether-1.4.0.tgz",
-      "integrity": "sha1-D5+hcfdb9YSF2BSelHmdeudNHBo="
-    },
     "text-table": {
       "version": "0.2.0",
       "resolved": "https://registry.npmjs.org/text-table/-/text-table-0.2.0.tgz",