Empty string after strip with opening block comment symbol inside of a comment

[a2937]

If a camper writes code like:

/**
 * Some comment text
 *  example.com/*  
 */

let hello = 'world';
console.log(hello);
`

All they will end up left with is an empty string.

I think we need a way for block comment characters to be escaped when they're already inside of a block comment.

Issue noted from: jonschlinkert/strip-comments#51