Push and "pull" would be more symmetric and intuitive to users.

[yuehhua]

In documentation,

julia> x = Signal(0)

julia> y = foldp(+, 0, x)

julia> push!(x, 1)

julia> value(y)
1

julia> push!(x, 2)

julia> value(y)
3

It use push! to push a value into the Signal, intuitively, we PULL a value out!
To be symmetric and intuitive, replace value() by pull() would be better.

[shashi]

We can definitely add pull as alias to value