Exponential to chi sq

[mkhattab940]

Test for relationship between exponential and chiSq. Fails with following log:

### Failure in: 6:RoundTrip:6:1:t_exponential_to_stdChiSq:0
haskell/Tests/TestTools.hs:130
expected:
chiSq_iid = fn n nat:
            fn mean real:
            fn stdev prob:
            q <~ plate _ of n: normal(mean, stdev)
            return summate i from 0 to size(q):
                   ((q[i] - mean) * prob2real(1/ stdev)) ^ 2
standardChiSq = fn n nat: chiSq_iid(n, nat2real(0), nat2prob(1))
standardChiSq(2)
but got:
q307 <~ normal(+0/1, 1/1)
q315 <~ normal(+0/1, 1/1)
return q307 ^ 2 + q315 ^ 2
Cases: 330  Tried: 283  Errors: 2  Failures: 17

### Failure in: 6:RoundTrip:6:1:t_exponential_to_stdChiSq:1
haskell/Tests/TestTools.hs:130
expected:
chiSq_iid = fn n nat:
            fn mean real:
            fn stdev prob:
            q <~ plate _ of n: normal(mean, stdev)
            return summate i from 0 to size(q):
                   ((q[i] - mean) * prob2real(1/ stdev)) ^ 2
standardChiSq = fn n nat: chiSq_iid(n, nat2real(0), nat2prob(1))
standardChiSq(2)
but got:
X3 <~ uniform(+0/1, +1/1)
return log(real2prob(X3)) * (-2/1)
Cases: 330  Tried: 284  Errors: 2  Failures: 18