numtest: add --silent and --verbose

To make travis-ci.org happy, make numtest print out a status report
every 60 seconds and silence after 100 warnings.

If there is more than 10 minutes of silence, travis-ci will abort the
test. Write a status message to keep tests alive (unless --silent).

If there is more than 4 megabytes of logs, travis-ci will kill the test.
Write only first 100 failure messages (unless --verbose).
Tweak .travis.yml

Disable email notifications, remove "branches" section which doesn't
work.
Orbit intercepts
WIP: Generate two intercepting orbits for testing
Fix intersects near apoapsis
True anomaly around ascending/descending node
Fix true anomaly around intersect
XXX: Fix non-coplanar intersects near apoapsis

THIS IS NOT CORRECT: seed 4719108 gives two intersects, only one is
correct.
Fix non-coplanar intersects around apoapsis
Clean up intersect code a little
Intersect apoapsis wrap only for closed orbits

Limit true intersect anomaly of hyperbolic orbits.
Find time intervals of possible intercepts
Fix time ranges at apoapsis
Intercept time intervals in order
Refactor intercept time ranges
intercept_minimize boilerplate
intercept_minimize WIP
Test intercept

Reduce maximum true anomaly of intercept position on hyperbolioc orbits.