Divorces may be granted for any of the following causes:
1.  Adultery.
2.  Extreme cruelty.
3.  Wilful desertion.
4.  Wilful neglect.
5.  Habitual intemperance.
6.  Conviction of felony.
7.  When either the husband or wife has become permanently insane, as provided in sections 32-801 to 32-805, inclusive.
8.  Irreconcilable differences.