Fixed build on Rust 1.0

Author: fizyk20

src/distributions/poisson.rs

@@ -43,7 +43,7 @@ impl Poisson {
     /// `lambda`. Panics if `lambda <= 0`.
     pub fn new(lambda: f64) -> Poisson {
         assert!(lambda > 0.0, "Poisson::new called with `lambda` <= 0");
-        Poisson { 
+        Poisson {
             lambda: lambda,
             exp_lambda: (-lambda).exp(),
             log_lambda: lambda.ln(),
@@ -64,7 +64,7 @@ impl IndependentSample<u64> for Poisson {
             let mut result = 0;
             let mut p = 1.0;
             while p > self.exp_lambda {
-                p *= rng.gen();
+                p *= rng.gen::<f64>();
                 result += 1;
             }
             result - 1