Move files to fix doc build
docs: Fix doc files
docs: Fix intro link

Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>
docs: Create _static and _templates directories

Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>
docs: Update documentation to include install guide

Now that we have Ubuntu PPAs and Fedora COPRs, we can
show people the easy way to test avocado.

Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>