Allow for easier use when trying to "reuse" the same discord.Embed
object by providing new methods such as Embed.clear_fields,
Embed.set_field_at, and allowing you to set things to Embed.Empty to
clear out an attribute.
For ease of use, things are automatically casted to ``str`` to prevent
the user from having HTTP 400 errors if they forgot to do so. The new
embed builder also supports "fluent-style" interface to allow you to
chain methods in a single line if necessary.
Certain parameters were removed since they were ignored by Discord
anyway such as `width` and `height` in Embed.set_image and
Embed.set_thumbnail.
