Fix path regex match bug

[Norris1z]

This change prevents Regex expression errors from being thrown when the paths passed to the function has a ++ in them.

Taking a path like some/dummy/path/with++/
the function transforms it to some\/dummy\/path\/with++\/ the second + is not ignored by the regex engine and hence throws an Invalid Regular Expression Error

This pull request changes the path to some\/dummy\/path\/with\+\+\/ with all + escaped.

I noticed the bug when i tried to run npm start in a directory containing a + in it's name.
npm version 5.5.1
node version 8.9.3

$ npm start

> demoreact@0.1.0 start C:\Users\Norris\Desktop\C_C++\JS\NodeJs\demoreact
> react-scripts start

Invalid regular expression: /^(?!C:\\Users\\Norris\\Desktop\\C_C++\\JS\\NodeJs\\demoreact\\src\\).+[\\/]node_modules[\\/]/: Nothing to repeat
npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! demoreact@0.1.0 start: `react-scripts start`
npm ERR! Exit status 1
npm ERR!
npm ERR! Failed at the demoreact@0.1.0 start script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.

Changing the path for the project solved the problem.

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[Timer]

How about using https://www.npmjs.com/package/escape-string-regexp?

[facebook-github-bot]

Thank you for signing our Contributor License Agreement. We can now accept your code for this (and any) Facebook open source project. Thanks!

[Norris1z]

@Timer thanks. I modified the code to use the package

[Timer]

Great, thanks much!

[gaearon]

This is out in react-scripts@1.1.0! Please let us know if something doesn’t quite work.
https://github.com/facebookincubator/create-react-app/releases/tag/v1.1.0