Setext Headings Error

[Stecyk]

The editor does not correctly display the results for example 51: https://github.github.com/gfm/#example-51

In the example, the resulting display should be an H1. Instead, it is plain text.

Here's my editor session:
https://jbt.github.io/markdown-editor/#jZFNasNADIX3OsWDLAqhsZNCNoYs0ybQ7nqBcazYgycjd37quKfv2GmaRShUMAyIp6dP0gwvOuxiiTfl2kp6i+2Z3UF7Jtqe1akzjPWqQBNC54s8r3VoYpn9fAc55fXxlM/4Il2sV6iEPawE9OJadE46dmZAyQcVPSM06fE5wDcSTZXyUBa7VUb0LIJ5qRyV6mtOmxREtP9VGpEWRrejh/ap0EgPbSfHSvvOqKEgmuFqg8mG6JXDg0dwA6LXtoZCpXyTKn1gVUGOkwN/RGXgdW3vSBYpks97UqlSPhmOfTQBCaJ3khyDSIb9lBgHH+d5yv5CZxzFJPSEMuLe89LeBk4tQlKY4RF8PcNyWqkv8O9rLG+jXBa6uWz1llxcg74B

# GitHub Markdown Exercise

Example 51: https://github.github.com/gfm/#example-51 does not work properly because the text should be an H1.

Foo *bar
baz*
====


It should look like this below in the display:

# Foo *bar baz*


Let's try using a dash instead of the equal sign.

Foo *bar
baz*
----


The above result is wrong too. It is not an H2.

It should look like the following:

## Foo *bar baz*



Interestingly, example 50 works:  https://github.github.com/gfm/#example-50

Foo *bar*
=========

Foo *bar*
---------