Format specifiers in f-strings don't highlight the entire thing in a consistent manner

Nobody has claimed this yet.

Hello. Sometimes the `:...` aspect of a format string is highlighted in its entirety but often times it's not. I would like to know if it's possible to make it so it's all under the same consistent scope or if it's by design that it doesn't. My main use case has to do with types using a custom `__format__`.

For example:


I would have imagined both of these to fall under the same scope but they're not.

The first screenshot goes `source.python` > `meta.fstring.python` > `storage.type.format.python`
The second screenshot goes `source.python` > `meta.function-call.python` > `meta.function-call.arguments.python` > `meta.fstring.python`

A regular line of code without using custom `__format__` (e.g. `{test:.2f}`) goes as `source.python` > `meta.function-call.python` > `meta.function-call.arguments.python` > `meta.fstring.python` > `storage.type.format.python` which is what I would expect the other two to return as well, unless it's meant to be treated differently.

* **Editor name and version**: Sublime Text 3.2.1 Build 3207
* **Platform**: Windows 8.1
* **Color scheme**: Custom
* **MagicPython version**: 1.1.1
* **A sreenshot**: See above
* **5-10 lines of surrounding code**: In the screenshot hopefully

Start by reproducing the two f-string examples in Sublime Text 3.2.1 with MagicPython 1.1.1 and inspect their syntax scopes, comparing them with the regular `{test:.2f}` example. Done means format specifiers in the reported cases receive a consistent scope, or the behavior is documented as intentional.

Written by the indexing model from the issue text.