Consider calling glm.fit() instead of glm()

[mbojan]

In

https://github.com/statnet/ergm/blob/1f4401ed73356cbf89c2f35fd35d6a981f4caea0/R/ergm.mple.R#L100-L101

consider calling glm.fit() directly rather than glm(). Experiments with biggish data show that it might cut the computing time by half.