spec.md: fixing some grammar/structure issues
spec.md: fixing some grammar/structure issues

Reading the spec was a pretty good experience until I hit this paragraph, which took kind of a wild leap into future tense, passive voice, and a run-on sentence. FIFY :).
ChengTiesheng/spec,tklauser/spec,krnowak/appc-spec,endocode/appc-spec,apcera/appc-spec,jonboulle/spec,3ofcoins/appc-spec,appc/spec,yifan-gu/spec,alban/appc-spec,tklauser/spec,stufflebear/spec,stufflebear/spec,yifan-gu/spec,alban/appc-spec,dgonyeo/spec,alban/appc-spec,endocode/appc-spec,3ofcoins/appc-spec,dustymabe/spec,krnowak/appc-spec,zenlinTechnofreak/spec,iaguis/appc-spec,3ofcoins/appc-spec,dustymabe/spec,jonboulle/spec,krnowak/appc-spec,tklauser/spec,jonboulle/spec,dustymabe/spec,dgonyeo/spec,craimbert/spec,ChengTiesheng/spec,appc/spec,ChengTiesheng/spec,iaguis/appc-spec,apcera/appc-spec,yifan-gu/spec,zenlinTechnofreak/spec,marineam/spec,apcera/appc-spec,squeed/spec,appc/spec,endocode/appc-spec,stufflebear/spec,squeed/spec,squeed/spec,dgonyeo/spec,craimbert/spec,zenlinTechnofreak/spec,marineam/spec,marineam/spec,craimbert/spec,iaguis/appc-spec