In Hosting section make it clearer that some sites host git but not hg.

[Mike Lake]

In the introduction it states "It is widely used, both because it’s easy to set up and because of a hosting site called Bitbucket." Bitbucket no longer host Mercurial repos and so this should probably be changed to "It is widely used and it’s easy to set up."

In the "Hosting" section it probably should be made clear that some of these services host both git and hg but some only host git repos. Below is a suggested change - I have added a sentence in the middle.
"Each of these services provides a web interface that enables people to create, view, and edit their code repositories. Some host Git and Mercurial repositories, some host only Git repositories. These services also provide communication and project management tools including issue tracking, wiki pages, email notifications, and code reviews."