Fix JSON pages not building on Windows (#611)
Fix JSON pages not building on Windows (#611)

* Check for .json file extension before JSON parse. Was throwing when reading js files.

* Fix cross platform regex

* Revert back to the original content in read-page.js

sedubois/next.js,azukaru/next.js,callumlocke/next.js,kpdecker/next.js,nikvm/next.js,flybayer/next.js,zeit/next.js,zeit/next.js,flybayer/next.js,giacomorebonato/next.js,azukaru/next.js,dizlexik/next.js,kevmannn/next.js,flybayer/next.js,azukaru/next.js,azukaru/next.js,arunoda/next.js,nahue/next.js,flybayer/next.js,BlancheXu/test,JeromeFitz/next.js,JeromeFitz/next.js,BlancheXu/test,JeromeFitz/next.js,zeit/next.js,nelak/next.js,JeromeFitz/next.js,BlancheXu/test