v0.2.0

Retry.jl used to use try/catch inside the catch block's @ignore if ...
condition. The purpose of this was to treat if conditions that throw
errors as false. e.f. @ignore if e.reason == "Foo" end might throw an
exception if e does not have a reason field. Retry.jl used to allow this
and treat it as false.

At present doing a nested try/catch in a catch block causes the Julia
stacktrace to be corrupted: JuliaLang/julia#19979 (comment)

After this commit, Retry.jl requires @ignore if ... conditions to return
true or false and not throw exceptions.

The ecode() function has been exported to allow replacing

@ignore if e.code == "404" end

with

@ignore if ecode(e) == "404" end