Add ruby.NewGemSpecCataloger to DirectoryCatalogers. (#1971)

* Add ruby.NewGemSpecCataloger to DirectoryCatalogers.

Signed-off-by: Evan <chaol@vmware.com>

* fixed tests

Signed-off-by: Evan <chaol@vmware.com>

* Addressed review comment

Signed-off-by: Evan <chaol@vmware.com>

* Remove NewInstalledGemSpecCataloger from default dir catalogers

Because the files that the installed gemspec cataloger work off of are a
subset of the files that the more general gemspec cataloger will work
off of, we shouldn't have both of them on by default, since this could
result in finding the same package twice.

Signed-off-by: Will Murphy <will.murphy@anchore.com>

---------

Signed-off-by: Evan <chaol@vmware.com>
Signed-off-by: Will Murphy <will.murphy@anchore.com>
Co-authored-by: Will Murphy <will.murphy@anchore.com>

test/integration/catalog_packages_cases_test.go

@@ -94,6 +94,7 @@ var dirOnlyTestCases = []testCase{
 			"arel":                 "5.0.1.20140414130214",
 			"bootstrap-sass":       "3.1.1.1",
 			"builder":              "3.2.2",
+			"bundler":              "2.1.4",
 			"coffee-rails":         "4.0.1",
 			"coffee-script":        "2.2.0",
 			"coffee-script-source": "1.7.0",
@@ -136,6 +137,7 @@ var dirOnlyTestCases = []testCase{
 			"turbolinks":           "3.0.0",
 			"tzinfo":               "1.2.0",
 			"uglifier":             "2.5.0",
+			"unbundler":            "3.1.4",
 			"unicorn":              "4.8.3",
 		},
 	},