find_package COMPONENTS

This reverts commit 02f31897.

Update issue 79
Added a test which uses gflags_declare.h as any other project would use it to avoid such avoidable build configuration mistakes.

Expose as few system variables as possible through public interface.
Perform STRIP_FLAGS_HELP test using CMake instead of Bash.
Change file path separator used by gflags_reporting.cc to backslash on Windwos.