Julia 1.0 upgrade of the package

I changed to "0.6 or later", because the previous versions built with 0.6 ...
however I think 0.7 or later is sufficient, because new projects
will be started with 1.0 anyway.

The issue seems to be with the function dot() which is Base.dot in 0.6 but
LinearAlgebra.dot in 0.7. Making it running for theo old and new package
manager ist possible but may be not worth the time to spend ...
If somebody needs 0.6, the previous version can be installed.

=> Therefore requirements changed to 0.7 or later