Fixes #22 added Graph[int].add_edges and Graph[float].add_edges

[LeeKamentsky]

Graph.add_edges takes any type and shape of Numpy array and casts each to what's called for in Graph._add_edges. If someone wants to be memory-efficient, they would make sure to use arrays of the correct type, but IMHO, most people will be more casual users and not care.

If you're wondering about the inner loop, Cython boils it down to this:

for (__pyx_v_idx = 0; __pyx_v_idx < __pyx_t_6; __pyx_v_idx++) {
     __pyx_t_7 = __pyx_v_idx;
     __pyx_t_8 = __pyx_v_idx;
    __pyx_t_9 = __pyx_v_idx;
    __pyx_t_10 = __pyx_v_idx;
    try {
      __pyx_v_self->thisptr->add_edge((*__Pyx_BufPtrStrided1d(__pyx_t_5numpy_uint32_t *, __pyx_pybuffernd_i.rcbuffer->pybuffer.buf, __pyx_t_7, __pyx_pybuffernd_i.diminfo[0].strides)), (*__Pyx_BufPtrStrided1d(__pyx_t_5numpy_uint32_t *, __pyx_pybuffernd_j.rcbuffer->pybuffer.buf, __pyx_t_8, __pyx_pybuffernd_j.diminfo[0].strides)), (*__Pyx_BufPtrStrided1d(__pyx_t_5numpy_int64_t *, __pyx_pybuffernd_capacity.rcbuffer->pybuffer.buf, __pyx_t_9, __pyx_pybuffernd_capacity.diminfo[0].strides)), (*__Pyx_BufPtrStrided1d(__pyx_t_5numpy_int64_t *, __pyx_pybuffernd_rcapacity.rcbuffer->pybuffer.buf, __pyx_t_10, __pyx_pybuffernd_rcapacity.diminfo[0].strides)));
    } catch(...) {
      __Pyx_CppExn2PyErr();
      {__pyx_filename = __pyx_f[0]; __pyx_lineno = 183; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
    }
  }

[pmneila]

Thank you!