Implement the debug flag and help command

I'm vacillating about the choice to have separate Config structs in the
`helm` and `run` packages. I can't tell whether it's "good separation of
concerns" or "cumbersome and over-engineered." It seems appropriate at
the moment, though.

internal/run/config.go

@@ -0,0 +1,22 @@
+package run
+
+import (
+	"io"
+)
+
+// Config contains configuration applicable to all helm commands
+type Config struct {
+	Debug          bool
+	KubeConfig     string
+	Values         string
+	StringValues   string
+	ValuesFiles    []string
+	Namespace      string
+	Token          string
+	SkipTLSVerify  bool
+	Certificate    string
+	APIServer      string
+	ServiceAccount string
+	Stdout         io.Writer
+	Stderr         io.Writer
+}