Log Message:
Update rubyzip to 1.2.0.

* Don't enable JRuby objectspace #252
* Fixes an exception thrown when decoding some weird .zip files #248
* Use duck typing with IO methods #244
* Added error for empty (zero bit) zip file #242
* Accept StringIO in Zip.open_buffer #238
* Do something more expected with new file permissions #237
* Case insensitivity option for #find_entry #222
* Fixes in documentation and examples