Update documentation for DOLFIN version 1.4.0
Update documentation for DOLFIN version 1.4.0
Update documentation for UFL version
Add documentation for FEniCS 1.4.0.
Add download button for 1.4.0 release.
Latest stable release is now 1.4.0.
Remove instructions for installing UFC.
Write ChangeLog for 1.4
Add ChangeLog for 1.4 to release notes index page.