Replacing is wrong if values or regexps contain $ character.

Hello!

I tried to use the plugin for replacing $$TEST$$ string in the code. The plugin didn't change anything.

Config example:
```
const ReplacePlugin = require('webpack-plugin-replace');
module.exports = {
// ...
plugins: [
new ReplacePlugin({
exclude: [
'foo.js',
/node_modules/,
filepath => filepath.includes('ignore')
],
values: {
'$$TEST$$': 'FOO',
}
})
]
};
```

Start by reproducing the reported configuration with a replacement key containing `$$TEST$$`, then inspect the plugin's replacement handling and any existing tests. Done means values or regular expressions containing `$` are replaced correctly without changing behavior for ordinary values.

Written by the indexing model from the issue text.