Add dep Go dependency management metadata files (#1544)

Adds the dep Go dependency management metadata files to the SDK. The Gopkg files allow your tools to detect the version of dependencies the SDK uses.

Non-runtime dependencies such as test, example, and code generation packages are excluded from the Gopkg files as they are not needed to use the SDK.

Fix #1451
Fix #634

Gopkg.toml

@@ -0,0 +1,48 @@
+
+# Gopkg.toml example
+#
+# Refer to https://github.com/golang/dep/blob/master/docs/Gopkg.toml.md
+# for detailed Gopkg.toml documentation.
+#
+# required = ["github.com/user/thing/cmd/thing"]
+# ignored = ["github.com/user/project/pkgX", "bitbucket.org/user/project/pkgA/pkgY"]
+#
+# [[constraint]]
+#   name = "github.com/user/project"
+#   version = "1.0.0"
+#
+# [[constraint]]
+#   name = "github.com/user/project2"
+#   branch = "dev"
+#   source = "github.com/myfork/project2"
+#
+# [[override]]
+#  name = "github.com/x/y"
+#  version = "2.4.0"
+
+ignored = [
+	# Testing/Example/Codegen dependencies
+	"github.com/stretchr/testify",
+	"github.com/stretchr/testify/assert",
+	"github.com/stretchr/testify/require",
+	"github.com/go-sql-driver/mysql",
+	"github.com/gucumber/gucumber",
+	"github.com/pkg/errors",
+	"golang.org/x/net",
+	"golang.org/x/net/html",
+	"golang.org/x/net/http2",
+	"golang.org/x/text",
+	"golang.org/x/text/html",
+	"golang.org/x/tools",
+	"golang.org/x/tools/go/loader",
+]
+
+
+[[constraint]]
+  name = "github.com/go-ini/ini"
+  version = "1.25.4"
+
+[[constraint]]
+  name = "github.com/jmespath/go-jmespath"
+  revision = "0b12d6b5"
+  #version = "0.2.2"