Fix default constructor for SizedArray

I ran into this problem working on a project that uses StaticArrays. I don't know the StaticArrays
codebase at all, so this may be wrong, but it has solved the problem for me.

Before this patch:

```
julia> StaticArrays.SizedMatrix{Tuple{2,2}, Float64}()
ERROR: MethodError: Cannot `convert` an object of type Type{Tuple{2,2}} to an object of type Array{Float64,2}
This may have arisen from a call to the constructor Array{Float64,2}(...),
since type constructors fall back to convert methods.
Stacktrace:
 [1] Type at /home/steve/.julia/v0.6/StaticArrays/src/SizedArray.jl:23 [inlined]
 [2] StaticArrays.SizedArray{Tuple{2,2},Float64,2,M} where M() at /home/steve/.julia/v0.6/StaticArrays/src/SizedArray.jl:31
```

After this patch:

```
julia> StaticArrays.SizedMatrix{Tuple{2,2}, Float64}()
2×2 StaticArrays.SizedArray{Tuple{2,2},Float64,2,2}:
 6.91502e-310  6.91504e-310
 6.91504e-310  0.0
```

My julia:

```
   _       _ _(_)_     |  A fresh approach to technical computing
  (_)     | (_) (_)    |  Documentation: https://docs.julialang.org
   _ _   _| |_  __ _   |  Type "?help" for help.
  | | | | | | |/ _` |  |
  | | |_| | | | (_| |  |  Version 0.6.0-pre.beta.338 (2017-04-26 15:52 UTC)
 _/ |\__'_|_|_|\__'_|  |  Commit 8e12b77 (2 days old master)
|__/                   |  x86_64-pc-linux-gnu
```

Author: gostevehoward

src/SizedArray.jl

@@ -20,7 +20,7 @@ immutable SizedArray{S <: Tuple, T, N, M} <: StaticArray{S, T, N}
     end
 
     function (::Type{SizedArray{S, T, N, M}}){S, T, N, M}()
-        new{S, T, N, M}(Array{T, M}(S))
+        new{S, T, N, M}(Array{T, M}(S.parameters...))
     end
 end