Add tests to cover all AFNI classes

[chrisgorgo]

The following afni classes have no tests:

• ThreedZcutup
• ThreedSkullStrip
• ThreedBrickStat
• Threedcalc
• ThreedAllineate

http://sourceforge.net/apps/trac/nipy/ticket/30

[tsalo]

@chrisfilo It looks like all of these have tests now. Can this be closed?

[chrisgorgo]

Sure!