Implement empty!() for CircularBuffer and add CircularBuffer to docs

[KadeG]

empty!(CircularBuffer) would be nicer to use than recreating it. CircularBuffer has auto-eviction while CircularDeque does not, so it warrants an entry in the docs.

[kmsquire]

Thanks for creating this issue. Do feel up to submitting a pull request?

[KadeG]

I'd love to. It may be terrible- I'm new to this.

[kmsquire]

No worries--I and others will try to give good feedback. Give it a try!

[KadeG]

CircularDeque's empty!() does not seem to actually delete anything. Is this faster than actually deleating things like in array.jl using _deleteend!(a::Vector, delta::Integer) = ccall(:jl_array_del_end, Void, (Any, UInt), a, delta) ?

Since CircularBuffer doesn't have n first, and last to reset, would recreating the buffer as an empty vector of type T work?

function Base.empty!(cb::CircularBuffer)
    cb.buffer = typeof(cb.buffer)[]
    cb
end

Sidenote: CircularDeque's docstring Create a double-ended queue of maximum capacity 'n' is a bit confusing because n is used as the number of elements currently contained in empty!(), not the maximum capacity.

[KadeG]

This is now #317 . Closing the issue.