support quote and space both in a string when parse string to context and hash

[creeperyang]

Related to #6 #7

We can parse context key="h\"i" and context key="h i" correctly. However, parsingcontext key="h\" i" is still incorrectly.

Support it in the future.

[creeperyang]

After much deliberation, I finally deside not to fix it:

1. Current features are enough, this feature does not worth the effort.
2. We can use other way to achieve this, such as key = 'h" i'.