Inline model field fix to address issues #417, #418

Missing "op" alias for os.path

Use `send_file` instead of `send_from_directory` to serve files in FileAdmin

Don't use column name for pk

Gets the attribute name of the model's pk column, rather than the
column's name (which can differ).

This probably needs to happen for inherited keys, too, but I have not
tested.

The path is already validated in `_normalize_path`. Also, `send_from_directory` abort paths with backslash, breaking FileAdmin subfolders in Windows.

With `send_file`, we have a minor issue with the download URL, it has path with backslash, but `_normalize_path` fix this before download.

Make FileAdmin.base_url optional.

Add a `FileAdmin.can_download` flag to enable download of uploaded files.
If `base_url` is not defined, a `.download` route will serve uploaded files.

Do not enforce github ribbon over http

Docs in readthedocs run over https and Chrome recognize the ribbon as unsafe content.

Inline view fix

Remove inline_view from contrib/peewee/form.py, so as to fix #406 (cleaned up this time)

This reverts commit c424c3fe.

This reverts commit 749161e7.

This reverts commit deb60c15.

form fix

errrors replaced with errors

Old format fltN_M still works, but the new format flt_name_operation coexists side-by-side.

Fix compat for CPython/PyPy 2.x

Support both __builtins__ as a dictionary and a module.

Allow custom _id value type in mongoengine backend