Implement Cobra CLI tooling, Viper config tooling (#336)

* start pulling out + replacing urfave and config

* replace many many instances of config

* move more stuff => viper

* properly remove urfave

* move some flags to root command

* add testrig commands to root

* alias config file keys

* start adding cli parsing tests

* reorder viper init

* remove config path alias

* fmt

* change config file keys to non-nested

* we're more or less in business now

* tidy up the common func

* go fmt

* get tests passing again

* add note about the cliparsing tests

* reorganize

* update docs with changes

* structure cmd dir better

* rename + move some files around

* fix dangling comma

vendor/github.com/spf13/afero/lstater.go

@@ -0,0 +1,27 @@
+// Copyright © 2018 Steve Francia <spf@spf13.com>.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package afero
+
+import (
+	"os"
+)
+
+// Lstater is an optional interface in Afero. It is only implemented by the
+// filesystems saying so.
+// It will call Lstat if the filesystem iself is, or it delegates to, the os filesystem.
+// Else it will call Stat.
+// In addtion to the FileInfo, it will return a boolean telling whether Lstat was called or not.
+type Lstater interface {
+	LstatIfPossible(name string) (os.FileInfo, bool, error)
+}