Fixing issue in local ensembles caused by PHP null parameters depreca…

…tion

Fixing both the upper and lowercase discrepancies in headers location

Fixing multimodel batch predictions

Fixing local models for datasets with text fields

- Fixing local prediction when text fields contains multigrams
- Fixing path in predicting functions
- Fixing typos
- Fixing tests
- Changing tests to github actions

Adding new test examples

Removing redundant test

Splitting tests and enlarging travis timeout

Fixing tests

added namespaces

Adding CHANGELOG file to store the version changes