Add additional default HTTP headers to better mimic NSURLRequest's behavior.
Public "metadata" string constants style cleanup.
Additional comments about default HTTP request headers.
Merge pull request #58 from kgoodier/add-http-headers

Add default HTTP headers
Split build into platform-specific frameworks
Merge pull request #57 from kgoodier/metadata-style-cleanup

Metadata style cleanup
Merge remote-tracking branch 'upstream/develop' into develop
Track bytes sent and received per request.

Each stream tracks on-the-wire bytes transmitted and received. This
accounts for all SPDY framing and stream-related control messages,
but does not factor in non-stream-related control messages.

These fields are not yet properly exposed to the application, as using
the metadata mechanism (adds to response headers) happens too soon,
before the body has been read and accounted for. tx_bytes should be
accurate, though.
Merge branch 'tx-rx-bytes' of https://github.com/kgoodier/CocoaSPDY into tx-rx-bytes