Refactor the `Decoder` to use the `HeaderTable`
Refactor the `Decoder` to use the `HeaderTable`

The `Decoder` struct now uses the `HeaderTable` instead of both
the DynamicTable and a static table. This refactoring cleans up
the implementation of the `Decoder` since now it just delegates
the indexing to the `HeaderTable`.

tempbottle/solicit,stepancheg/solicit,gwicke/solicit,Galvanization/solicit,jinnjuice/solicit,mlalic/solicit