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/viper/internal/encoding/yaml/codec.go

@@ -0,0 +1,14 @@
+package yaml
+
+import "gopkg.in/yaml.v2"
+
+// Codec implements the encoding.Encoder and encoding.Decoder interfaces for YAML encoding.
+type Codec struct{}
+
+func (Codec) Encode(v interface{}) ([]byte, error) {
+	return yaml.Marshal(v)
+}
+
+func (Codec) Decode(b []byte, v interface{}) error {
+	return yaml.Unmarshal(b, v)
+}