List bugs in Markdown parser

[KristofferC]

Changing the list type should give separate lists:

julia> typeof.(Markdown.parse(
       """
       * foo
       + bar
       """).content)
1-element Array{DataType,1}:
 Base.Markdown.List

Spaces on an empty line between list items breaks a list in two:

julia> typeof.(Markdown.parse("  * dsadsa\n\n  * dsadas\n").content)
1-element Array{DataType,1}:
 Base.Markdown.List

julia> typeof.(Markdown.parse("  * dsadsa\n  \n  * dsadas\n").content)
2-element Array{DataType,1}:
 Base.Markdown.List
 Base.Markdown.List

[jpfairbanks]

Here is another one JuliaDocs/Documenter.jl#900:

julia> using Markdown
¨
julia> s = """
       ---
       abstract: |
           This is the abstract
       author:
       - |
           Document Authors
       date: 'Dec 1, 2018'
       title: |
         The Title
       ---
       """;

julia> Markdown.parse(s)
ERROR: BoundsError: attempt to access 0-element Array{SubString{String},1} at index [1]
Stacktrace:
 [1] getindex at ./array.jl:731 [inlined]
 [2] (::getfield(Markdown, Symbol("##55#57")){Base.GenericIOBuffer{Array{UInt8,1}},Markdown.MD})() at /Users/osx/buildbot/slave/package_osx64/build/usr/share/julia/stdlib/v1.0/Markdown/src/GitHub/table.jl:48