Unify request/response roles of Compressor/Decompressor

Latest HPACK spec has no distinction between request and response.
Merge pull request #20 from lepidum/unify-compressor-req-res

Unify request/response roles of Compressor/Decompressor
Framer updated for h2-14

- 24-bit frame size
- Default max frame size is 16384, not 16383
- Setting identifier is now 16-bit
- Remove PAD_HIGH, padding in CONTINUATION
- Allow extension frames, extension settings
Stream updated for h2-14

- Priority parameters are weight, stream_dependency, exclusive
- Stream statemachine adjusted for h2-14
- PRIORITY after stream close allowed
- Header block continuation handling
- Splitting large frame into smaller (DATA, HEADERS, PUSH_PROMISE)
- Pseudo headers at the beginning
Readability improvement
Fix mandatory keyword arguments so that they work with Ruby 2.0.0
Add comment about stream dependency tree
Readability improvement
Merge pull request #21 from lepidum/draft-14-framer-stream

Draft 14 framer stream