Don't transform modules with import/export

[Rich-Harris]

Even if they contain CJS features like require, global etc. Ref #88 (comment)

[talmobi]

Had this issue with the recently released newest version of redux@3.6.0 (https://github.com/reactjs/redux/releases) which updated its symbol-observable dependency to version 1.0.2 (https://github.com/blesh/symbol-observable/blob/master/CHANGELOG.md) with es6 support.

A temporary fix is to simply ignore symbol-observable specifically as an exclude field in the commonjs plugin.

I just want to say that I tested this PR and it worked out of the box with the newest version of redux@3.6.0 and its updated symbol-observable dependency (and as a result fixed my build and dev npm scripts)

People using redux with the hat character ^ in their dependencies (like I did) will at some points auto update to 3.6.0 and come across this issue that this PR seems to fix.

The only there difference is that using this PR rollup-plugin-version logs out a message when running rollup/build script (not an error)

The `this` keyword is equivalent to `undefined` at the top level of an ES module, and has been rewritten

Other than that everything seems to be working the same.

references: benlesh/symbol-observable#21

[TrySound]

@talmobi You don't need this plugin anymore to build redux. Just set rollup option context: 'window'.

[talmobi]

Ahh, very good, thanks -- still need the plugin for other libraries though, and unless you exclude symbol-obvservable you get the build error without this PR.

[danbucholtz]

I have verified that this fixes #100

[benlesh]

Thanks for your work on this @Rich-Harris

[Rich-Harris]

Sorry for the delay everyone! Just released this as 5.0.0 since it's potentially a breaking change, along with another PR (#106) which should bring bundle sizes down a bit.