*: add basic implementer's guide
*: add basic implementer's guide

This is a first cut at #63, providing some suggested/best practices that
developers can follow to provide efficient and usable implementations of
the appc spec.

alban/appc-spec,dustymabe/spec,squeed/spec,alban/appc-spec,tklauser/spec,craimbert/spec,marineam/spec,tklauser/spec,3ofcoins/appc-spec,ChengTiesheng/spec,zenlinTechnofreak/spec,apcera/appc-spec,appc/spec,dgonyeo/spec,krnowak/appc-spec,endocode/appc-spec,3ofcoins/appc-spec,apcera/appc-spec,craimbert/spec,yifan-gu/spec,iaguis/appc-spec,endocode/appc-spec,appc/spec,3ofcoins/appc-spec,ChengTiesheng/spec,krnowak/appc-spec,dgonyeo/spec,stufflebear/spec,iaguis/appc-spec,krnowak/appc-spec,dustymabe/spec,apcera/appc-spec,jonboulle/spec,ChengTiesheng/spec,dgonyeo/spec,jonboulle/spec,zenlinTechnofreak/spec,yifan-gu/spec,endocode/appc-spec,stufflebear/spec,jonboulle/spec,yifan-gu/spec,dustymabe/spec,stufflebear/spec,tklauser/spec,appc/spec,squeed/spec,marineam/spec,craimbert/spec,iaguis/appc-spec,squeed/spec,marineam/spec,zenlinTechnofreak/spec,alban/appc-spec