Rename .jsx files to .js

[nathanmsmith]

Context

Recently, I came across an issue where the contributors of create-react-app advocated for dropping .jsx extension for the .js extension. I started to do this in a new branch, but then came across a linter error and found that airbnb prefers use of the .jsx syntax. I wanted to open it up for discussion of which file extension we want to use. Personally, I'm in the .js camp as that seems to be more popular and gaining traction.

[binerys]

If it doesn't really affect our build system (looks like webpack will easily handle the .js version), I'm with the use of .js. Simplicity and consistency is better in the end.