Extend ability to process image from disk to from disk and memory

[jingchaoluan]

Now the code can only process image coming from disk (image path) directly, but sometimes we need to process an image from memory (such as an image object or a file-like object).

Expected Behavior

@Checks() function before functions 'read_image_gray()' and 'read_image_binary()' can not only pass 'string' type image (image path coming from disk), but also pass 'object' type image (image object coming from memory)

Current Behavior

For code lines (#155, #194) @Checks() before functions 'read_image_gray()' and 'read_image_binary()', the current parameter value 'str' in @Checks() indicates that only a 'string' type image (the image path in local disk) can pass the checks() function and then be read. It will limit the code can only process image coming from disk.

Possible Solution

On code lines #155 and #194, change the first parameter value in @Checks() from 'str' to '{str, object}'. Thus for images coming from memory (objects) can also be check correctly and then be read.

Steps to Reproduce (for bugs)

Your Environment

• Python version: 2.7.12

• Git revision of ocropy: ebd8235
• Operating System and version: Ubuntu Linux 16.04

[zuphilip]

Pull request is here: #260