Erlang distribution documentation should show cdf/pdf or at least point out the difference to the cdf/pdf given by wikipedia

[theplatters]

Distributions.jl/src/univariate/continuous/erlang.jl

Lines 1 to 16 in aad64af

	"""
	Erlang(α,θ)
	The *Erlang distribution* is a special case of a [`Gamma`](@ref) distribution with integer shape parameter.
	```julia
	Erlang() # Erlang distribution with unit shape and unit scale, i.e. Erlang(1, 1)
	Erlang(a) # Erlang distribution with shape parameter a and unit scale, i.e. Erlang(a, 1)
	Erlang(a, s) # Erlang distribution with shape parameter a and scale s
	```
	External links
	* [Erlang distribution on Wikipedia](http://en.wikipedia.org/wiki/Erlang_distribution)
	"""

References the wikipedia page and gives a description of the parameters, (where the names given in the function signature differ from the names of the parameters in the docstring). However this is not consistent, because the function uses the reciprocal of the parameter lambda, which is never pointed out.

[theplatters]

I have added a pull reques #1915