Changes to source code to make it run on Linux + instructions

[zoro11031]

There were some issues with the source code preventing it from compiling and running on Linux, made some minor changes to ocr_space.py and ocr.py and also added some instructions to ensure user has all required dependencies and can install the application to be easily launched

[mathewthe2]

Haven't run it on linux yet, but I suppose there is an issue with the space_ocr module on linux?