Documentation tweaks (`map!()` and `names()`)
Tweaks to StepRange: Take 2
deprecate readsfrom/writesto in favor of simply using open on AbstractCmds, and support: open(cmd, mode) do io ... end
better rearrangement of try/catch block in open(f, cmds)
fix #6672 (better reducedim type inference)
tweaks of the sum functions.

Introduce subzero, add zero, etc to enhance consistency & efficiency.
merge three sum{T}(a::AbstractArray{T) for different kinds of T into a single method
specialize of sum(x) when x is a number
minor fix of addzero(::AbstractArray)
make `sum(x::Number) = x`
Merge pull request #7013 from lindahua/dh/sum2

Tweaks of sum functions
Merge pull request #6994 from stevengj/reducedim_type

better reducedim type inference
fix #7012, :: on array assignment LHS
Merge branch 'master' of github.com:JuliaLang/julia
Refactor sum functions

Now `sum(x)`, `sum(f, x)`, `sumabs(x)`, and `sumabs2(x)` use the same core algorithms. The function `sumabs` will be used to implement `vecnorm1`, and `sumabs2` will be used to implement `var`.
New sumabs2 to replace the original one in statistics.jl
some minor doc updates
remove cell.jl, simplify map on tuples
add tests for sumabs and sumabs2
Merge pull request #7017 from lindahua/dh/sum3

Refactoring sum functions