BUG: Remove babel-loader dependency
BUG: Remove babel-loader dependency

Left over from previous webpack explorations. Can cause dependency resolution
issues like:

  $ npm install
  [...]
  └── UNMET PEER DEPENDENCY webpack@1 || 2 || ^2.1.0-beta || ^2.2.0-rc

  npm WARN babel-loader@6.4.1 requires a peer of webpack@1 || 2 || ^2.1.0-beta
  || ^2.2.0-rc but none was installed.

Also update babel-core and babel es2015 preset packages.

thewtex/ITKBridgeJavaScript,InsightSoftwareConsortium/ITKBridgeJavaScript,thewtex/ITKBridgeJavaScript,InsightSoftwareConsortium/ITKBridgeJavaScript,InsightSoftwareConsortium/ITKBridgeJavaScript,thewtex/ITKBridgeJavaScript