Create a Lint step [#3]

Still need global flags and checks for mandatory settings, but the basic
functionality is there.

internal/run/lint.go

@@ -0,0 +1,28 @@
+package run
+
+import (
+// "fmt"
+)
+
+// Lint is an execution step that calls `helm lint` when executed.
+type Lint struct {
+	Chart string
+
+	cmd cmd
+}
+
+// Execute executes the `helm lint` command.
+func (l *Lint) Execute(_ Config) error {
+	return l.cmd.Run()
+}
+
+// Prepare gets the Lint ready to execute.
+func (l *Lint) Prepare(cfg Config) error {
+	args := []string{"lint", l.Chart}
+
+	l.cmd = command(helmBin, args...)
+	l.cmd.Stdout(cfg.Stdout)
+	l.cmd.Stderr(cfg.Stderr)
+
+	return nil
+}