Added documentation example for combining InferenceData (#552) and also solving the issue of creaton of empty file for better behaviour with inference data(#486)

[Shashankjain12]

Added example in the docstring as per the issue number #552

[Shashankjain12]

Why travis-ci is failing to build as my all test cases are solved except python3.6 lint?

[Shashankjain12]

Better behavior with empty InferenceData #486

• Added the code for empty file create according to issue Better behavior with empty InferenceData #486
• Created the test cases for that particular issue Better behavior with empty InferenceData #486
• Added comments for the if-else case

[canyon289]

@Shashankjain12 I hate to be the bearer of bad news

1. This issue is already in progress here, in good faith I can't accept this PR because someone else is already putting effort into it. Before taking on an issue please double check if someone else is working on it
2. Try and do one PR per issue. It makes it much easier to sort things out, large PRs are hard to manage and comment on

My suggestion would be to close this PR and just add documentation for combining inference data

#577

[Shashankjain12]

Ok sure I will close this PR