Add EIGENPY_SITELIB_ROOT to customize sitelib install location.

[seanyen]

This is a pull request to port a patch from eigenpy-feedstock. In conda configuration, the Python modules and the native library doesn't share the same install prefix. Hope we can add some flexibility to customize where to place Python modules in CMake files.

[seanyen]

There was a travis-ci build timeout so I trigger another round.

[jcarpent]

OK. You can also do a git commit --amend to avoid a new commit ;)

[jcarpent]

@seanyen Do you need a new release now?

[nim65s]

There is also a "Restart build" button, but I guess it is not accessible by everyone.

[seanyen]

@jcarpent if you have bandwidth for a new release, that would be fantastic. I really appreciated your time. :)

I didn't know the git commit --amend trick. Every day I learned something new.

[jcarpent]

@seanyen Can you handle the conda forge?

[gabrielebndn]

The easiest way to trigger a new CI is to close the PR and reopen it

[seanyen]

@seanyen Can you handle the conda forge?

Sure, I am on it now.

[wxmerkt]

There is also a "Restart build" button, but I guess it is not accessible by everyone.

It is accessible as soon as you login.