[BUGFIX] Support edge-case URLs of secondary Asset files

For example, an URL like `/file.css?#iefix` would cause an error when attempting to copy the file `/file.css` which you have invalid chars appended to the name.

Fixes: #216
[TASK] Support relative secondary Asset files in inline CSS
[TASK] Shorten regular expression for detecting file names
Merge pull request #232 from NamelessCoder/regexfilename

[BUGFIX] Support edge-case URLs of secondary Asset files