improve progress reporting

Improve reporting. (#22)

Rewrote reporting, also allowing a time gap between consecutive reports.

Additional minor fixes: wrap included test files into sets, doc fixes.

API redesign for LogDensityProblems.

v1.0.0

bump version

Update for Julia 1.0, code cleanup.

Major release before API change.

initial release

This is a very preliminary release. API changes will happen. Use strict upper bounds for version requirements.