Updated API, added tests, docs, export_html method and generate_html method

[Prakriti-nith]

Right now, data is converted in the form of html table. I have shifted it to javascript array for the further server-side implementation (as datatable can take Array of Array). I will execute the server-side implementation (to load large set of data piece by piece) in this PR too. Parallel changes will be done accordingly in daru-datable in a separate PR.
I am also trying to resolve this issue. In this PR data is set correctly in the javascript array but the column names are overlapping for multiple tables.

[Prakriti-nith]

This PR runs in parallel with changes in daru-data_tables#20. Those changes are not reflected here and will be seen after that PR gets merged. So some of the test cases failed due to that.
Fixes issue daru-data_tables#19. Now, datatable is working fine with javascript array as:

[Prakriti-nith]

I have updated the implementation to load a large set of data here. As the changes are in parallel in both the PRs, some of the tests will not pass.

[Prakriti-nith]

I haven't added tests for generate_html as generate_html and export_html_file will then have the redundant tests. I am adding the tests for to_html in daru-data_tables.

[coveralls]

Pull Request Test Coverage Report for Build 609

• 37 of 99 (37.37%) changed or added relevant lines in 2 files are covered.
• 14 unchanged lines in 3 files lost coverage.
• Overall coverage increased (+0.6%) to 97.608%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
lib/daru/view/adapters/datatables.rb	2	12	16.67%
spec/adapters/datatables_spec.rb	35	87	40.23%

Files with Coverage Reduction	New Missed Lines	%
lib/daru/view/adapters/datatables.rb	1	93.55%
spec/table_spec.rb	6	100.0%
spec/adapters/datatables_spec.rb	7	100.0%

Totals
Change from base Build 608:	0.6%
Covered Lines:	1061
Relevant Lines:	1087

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💛 - Coveralls

[Shekharrajak]

I haven't added tests for generate_html as generate_html and export_html_file will then have the redundant tests. I am adding the tests for to_html in daru-data_tables.

We should have testcases calling datatables adaptor here as well.

[Prakriti-nith]

@Shekharrajak I have added the test cases in this PR also.

[Prakriti-nith]

In this PR, I have updated the API, added docs and tests and added export_html and generate_html methods.
Below are the screenshots of the examples:

[Shekharrajak]

Looks good to me.

Please write examples and update the Wiki page accordingly.

Thanks!