v++ and changed tracking of infection events

added SR class to test initial infections in SIR

some modifications for epidemics

added weighted SIR test

fixed bugs

added classes to simulate gillespie on weighted static networks

added first SEIR base class

address #23

added possibility to save infection events in cluster-size-SIS

added get/set node status for SIS

mistake in sampling procedure

new SIS functionality

changed sampling behavior

updated docs for markov integration

use correct version of markov equation