Remove bindata_assetfs.go from git

Maintaining this file as part of git tree isn't great, it's not really possible to review changes to it, let's just build it locally, especially that we've added webpack that also builds all assets and it's the files generated by webpack that we now compile into bindata_assetfs.go

.gitignore

@@ -5,3 +5,4 @@ assets/static/dist
 node_modules
 .coverage
 .tests
+bindata_assetfs.go

CONTRIBUTING.md

@@ -47,16 +47,6 @@ JS modules are written using [CommonJS](http://www.commonjs.org/specs/modules/1.
 syntax. Webpack will use [babel](https://babeljs.io/) to transform JS code to
 [ES2015](https://babeljs.io/docs/plugins/preset-es2015/).
 
-Once assets dir is modified please run:
-
-    make bindata_assetfs.go
-
-This will rebuild [https://github.com/elazarl/go-bindata-assetfs](binary assets)
-file. Be sure to include it in the commit.
-Same applies to HTML template files, please rebuild bindata_assetfs.go before
-commit. Note that Makefile targets are setup to run it automatically if changes
-are detected, so it's usually not needed for development.
-
 During development you can set `NODE_ENV=test` before running any make targets,
 this will prevent webpack from using expensive optimizations only needed when
 generating production assets.