Commented Unassigned: Can't open some xlsx files [15036]

I receive from some people strange xlsx file, that I could not open with EPPlus.
After investigation I found, that some files in xlsx archive with wrong case. For example: "SharedStrings.xml", instead of "sharedStrings.xml".
Also all xml files info that archives have Whitespaces (indentation of xml)

I will make pull request soon
Comments: Pull Request: https://epplus.codeplex.com/SourceControl/network/forks/RoninDev/epplus/contribution/7135