Final changes for the 3.0 release

[giovannipizzi]

Tasks for preparing the release

• Make sure the new version number is written everywhere (Makefile, User guide, tutorial, README, and there is a string in io.F90
• Fix readme of examples of tutorial (~3 examples are missing)
• Decide if we want to avoid putting the compiled PDFs on git and instead e.g. using travis+github pages for them [probably for this release we keep as it is now]
• Add arXiv reference of paper [moved after release in Add reference of new paper (arXiv) for v3 #240]
• If needed update the date of the release (code header, User guide, tutorial, README, ...) - think also if we need to keep the date in so many places
• Double check that the pw2wannier90.f90 file did not change in the main repository of Quantum ESPRESSO (see Update pw2wannier90 to QE #231)
• Update the CHANGELOG with the few remaining commits after (and including some of) Jan 18th
• Fix release date in docs, parameters.F90, ...
• Check if it is safe to rename post_6.3 to 6.4 (or if we should do it right after the release: make an issue, then)
• Fix make dist to use git archive
• Check if the copyright lines are all updated if they refer to the year
• Update the PDF of tutorial, user_guide and solutions
• Update the FORD documentation [moved to New website  #114]
• Update the website
• Tag the release, possibly releasing a version of the .tar.gz released with the Makefile to be a bit slimmer
• Fix make dist to use the git tag
• Prepare compiled docs (3 PDF), and FORD documentation
• Make sure the new QE will link to the new release

[VVitale]

Once #233 is accepted I will open an other PR fixing some of the points above.