Unnecessary comment.
Allow '_id' as a general document field.

Wrong assumtion by test_post_custom_idfield that, if _id was not a IDFIELD,
then it would not be present in the document.
MarkupSafe 0.21
Small typo.

I feel bad for sending you these single-character changes. On the plus side, someone is reading your documentation! :)
Corrected default_sort example

The given example was causing a syntax error.
One more correction to default_sort example

On my previous commit, I had fixed the syntax error but completely missed how the sorting syntax actually worked.
Merge pull request #324 from jenmontes/patch-1

Small typo
Documentation improvements.