Shared array example needs fixing

[mbeltagy]

In https://github.com/JuliaLang/julia/blob/master/doc/manual/parallel-computing.rst

The example provided

S = SharedArray(Int, (3,4), init = S -> S[myid()-1:nworkers():length(S)] = myid())

produces an exception in 0.3.5

exception on 1: ERROR: BoundsError()
 in setindex! at array.jl:323
 in setindex! at sharedarray.jl:215
 in anonymous at none:1
 in anonymous at multi.jl:660
 in run_work_thunk at multi.jl:621
 in run_work_thunk at multi.jl:630
 in anonymous at task.jl:6

It seems that in the latest implementation myid() could start at 1 and hence a bounds error happens.
This could be a possible fix.

 S = SharedArray(Int, (3,4), init = S -> S[myid():nworkers():length(S)] = myid())

[ViralBShah]

Cc: @amitmurthy

[amitmurthy]

Thanks @mbeltagy . Fixed in master, should be backported in the next 0.3 release.