Remove bower components from source tree

All bower components should be fetched with `bower install`.
A `.bowerrc` file is added to specify the drop location for
the components.
The currently used versions of the components are added to
the `bower.json` file.

Author: timofurrer

.bowerrc

@@ -0,0 +1,3 @@
+{
+  "directory": "src/bower_components"
+}

.gitignore

@@ -59,3 +59,6 @@ target/
 
 # SASS cache
 .sass-cache
+
+# bower components
+src/bower_components

bower.json

@@ -22,10 +22,10 @@
   ],
   "dependencies": {
     "d3": "~3.5.5",
-    "threejs": "*",
-    "jquery" : "*",
-    "bootstrap": "*",
-    "requirejs" : "*"
+    "threejs": "r71",
+    "jquery" : "~2.1.4",
+    "bootstrap": "~3.3.4",
+    "requirejs" : "~2.1.18"
   },
   "devDependencies": {
     "jasmine": "~2.3.4"