Put step-specific config in those steps [#61]

This is just something that's been bugging me for a while--they're
specific to Lint and Upgrade, so that's where they belong.

internal/run/lint_test.go

@@ -80,16 +80,15 @@ func (suite *LintTestSuite) TestPrepareRequiresChart() {
 func (suite *LintTestSuite) TestPrepareWithLintFlags() {
 	defer suite.ctrl.Finish()
 
-	cfg := Config{
+	cfg := Config{}
+
+	l := Lint{
+		Chart:        "./uk/top_40",
 		Values:       "width=5",
 		StringValues: "version=2.0",
 		ValuesFiles:  []string{"/usr/local/underrides", "/usr/local/overrides"},
 	}
 
-	l := Lint{
-		Chart: "./uk/top_40",
-	}
-
 	command = func(path string, args ...string) cmd {
 		suite.Equal(helmBin, path)
 		suite.Equal([]string{"lint",