Custom glob options fix

Custom glob options are getting overrides by defaults.

Pretty print and preserve duplicates.

Output formatting via space parameter added, preserving duplicates in an array if duplicates:true instead of overriding existing value.

Support for "prefixFileName" function

When installed version 1.0.19, it will provide the support for custom "prefixFileName" function.
Credits to @pwachala.

BOM characters handling

#22 issue fix

File Extn Check Removed

Input file to merge need not be of .json extention, any file can be passed as an input as long as its content is strictly json format.
For further details check #37

Webpack 4 Deprecated Api fixes

Code modified to support Webpack4 and backward compatibility.

prefixFileName

New option prefixFileName added.
If true , the plugin will wrap the content of individual files with the corresponding file name as key and merge with result.

 sign_in.json
   {  
      "submit": "Sign in"
   }
sign_up.json
   {
     "submit": "Sign up" 
   }

Result:

{ 
    "sign_in": { 
        "submit": "Sign in"
    }, 
    "sign_up": { 
        "submit": "Sign up"
    }
}