code standards
API: normalize both key and value before calculating OAuth signature

The OAuth spec indicates that the full query string should be URL
encoded. The array_walk method does not change keys so when used with a
parameter like `filter[period]=week`, the key is not properly encoded.
This fixes that by properly encoding both the key and value.
API: double-encode percent symbols when normalizing parameters
Merge pull request #5270 from maxrice/master

Normalize both key and value before generating OAuth signature