Added configuration item to specify how to include the original header file.
This is useful when mocking a header file that is not local.  For example, if the header file to mock is accessible from <mymodule/myfile.h>, one could set the include format to '<mymodule/%s>'.
The default format is '"%s"', which keep the previous behavior.
Merge pull request #37 from jlesage/orig_header_include_format

Added configuration item to specify how to include the original header file