Use common standard test files

[vvasuki]

It makes much sense to use the same tests across transliteration modules in various languages. For this reason, https://github.com/sanskrit-coders/indic-transliteration/blob/master/src/test/resources/transliterationTests.json is also used at https://github.com/sanskrit-coders/indic_transliteration/tree/master/tests/data . How can we fix js tests to use a copy of this file as well?

I lack sufficient js experience - It would be great if someone like @rramphal or @psvenk could take this up. Makes adding new features/ symbols a lot less hairy.