Zipios++ version 2.1.1 published

This version includes a few fixes that were made here and there.

However, this new version is being uploaded because there were two uninitialized variable members found by Coverity. Probably not a problem since the tests did pass just fine, but it is always cleaner to have the correct everything all the time.

• Fixed a couple of classes initializations that were missing.
• Fixed a view system() call of which return values were not checked.
• Added a BUILD_ZIPIOS_TESTS cmake option flag.
• Fixed reference to README as README.md as it is called now.
• Allow for ZIPIOS_WINDOWS to compile under MS-Windows.
• Added an ssize_t definition for Windows.
• Removed the "catch_" prefix from all test names.
• Fixed some copyright notices.
• Cleaned up the coverage script.
• Added the BUILD_SHARED_LIBS and BUILD_DOCUMENTATION options to cmake.
• Fixed the FindZipIos.cmake file so it uses the correct names.
• Also make the destination directory for FindZipIos.cmake a variable.
• Enhanced the installation directory handling in cmake.