fixed rounding error in arraysplit

this patch fixes the following error:

julia> arraysplit(randn(1,584752),4096,2048)
ERROR: BoundsError()
 in copy! at array.jl:54

julia> versioninfo()
Julia Version 0.3.0-prerelease+2078
Commit 00ca83c* (2014-03-17 22:41 UTC)
Platform Info:
  System: Linux (x86_64-redhat-linux)
  CPU: Intel(R) Xeon(R) CPU           E5645  @ 2.40GHz
  WORD_SIZE: 64
  BLAS: libopenblas (USE64BITINT DYNAMIC_ARCH NO_AFFINITY)
  LAPACK: libopenblas
  LIBM: libopenlibm

julia> Pkg.status()
9 required packages:
 - ClusterManagers               0.0.1
 - DSP                           0.0.1+             master
 - Debug                         0.0.0
 - Devectorize                   0.2.1
 - Distributions                 0.4.2
 - MAT                           0.2.3
 - PyPlot                        1.2.2
 - Stats                         0.1.0
 - WAV                           0.2.2
11 additional packages:
 - ArrayViews                    0.4.1
 - BinDeps                       0.2.12
 - Color                         0.2.8
 - HDF5                          0.2.20
 - NumericExtensions             0.5.6
 - PDMats                        0.1.1
 - Polynomial                    0.1.1
 - PyCall                        0.4.2
 - StatsBase                     0.3.9
 - URIParser                     0.0.1
 - Zlib                          0.1.5