[jss-pseudo] Support a short notation for pseudo selectors

[kof]

Why?

• Sometimes we don't need all the features jss-nested provides
• Most other cssinjs libs use ":hover" syntax
• jss-isolate would be able to detect pseudo rules and avoid double isolation for those #698

How? We can check existence of ":" same way we check "&" and add a parent selector before it when extracting to a separate rule.

Another idea: write jss-pseudo plugin and put this functionality into a separate repository. So one can decide if they want to use jss-nested. Potentially we can completely avoid jss-nested by using jss-pseudo + jss-global.

[kof]

This one is also important when used together with jss-isolate, to avoid isolation of pseudo rules.