test tmrca moments
update test tmrca with bl comparisons
editing tests files, and running tests for tmrca, and number of segregating sites and recombinations
modify testing scripts
small modification to the test file
test for the migration option
improves seeding for mersenne twister

- switch to c++11
update virtual functions
update virtual functions, making corrections, and declared in forest.h and defined in forest.cc
adds documentation
Merge branch 'master' into single_migration
corrects migration rates after population splits