fixed some memory leaks with expr_free, switched to g_malloc and g_free

removed .travis.yml apt-get install libglib2.0-dev b/c already latest version
fixed memory leaks with not freeing items in lists of expr_s
switched to using glib functions for malloc and free
modified manager to g_malloc double a and b so expr_free can free it, a_num
and b_num are now double*s
removed old validator_test.c