Implement .rpm package gulp task

.rpm packages can now be build with:

    gulp vscode-linux-<arch>-build-rpm

The resulting package will be output to ~/rpmbuild/RPMS/<arch>/ and can be
installed on a Red Hat-based distro with:

    yum localinstall <path>

Note that Debian systems can build the package after installing the 'rpm'
package:

    apt-get install rpm

This was tested building 64-bit on Ubuntu 15.10 and installing on CentOS 7.

Fixes #3595

resources/linux/rpm/code.spec.template

@@ -0,0 +1,29 @@
+Name:     @@NAME@@
+Version:  @@VERSION@@
+Release:  @@RELEASE@@
+Summary:  Code editing. Redefined.
+License:  MIT
+URL:      https://code.visualstudio.com/
+Requires: git
+AutoReq:  0
+
+%description
+Visual Studio Code is a new choice of tool that combines the simplicity of a code editor with what developers need for the core edit-build-debug cycle.
+
+%install
+mkdir -p %{buildroot}/usr/bin
+cp -r usr/bin/@@NAME@@ %{buildroot}/usr/bin
+mkdir -p %{buildroot}/usr/share/@@NAME@@
+cp -r usr/share/@@NAME@@/* %{buildroot}/usr/share/@@NAME@@
+mkdir -p %{buildroot}/usr/share/applications
+cp -r usr/share/applications/@@NAME@@.desktop %{buildroot}/usr/share/applications
+mkdir -p %{buildroot}/usr/share/pixmaps
+cp -r usr/share/pixmaps/@@NAME@@.png %{buildroot}/usr/share/pixmaps
+
+%files
+%defattr(-,root,root)
+
+/usr/bin/@@NAME@@
+/usr/share/@@NAME@@/
+/usr/share/applications/@@NAME@@.desktop
+/usr/share/pixmaps/@@NAME@@.png