Modify folder structure

Existing folder structure was modified to be more in line with Python
packaging style.
Set correct path for module import

Modified to reflect the correct path when importing modules due to
change in path of the folders.

Additionally add new line at EOF.
Create `tests` folder

Create `tests` folder to contain all the unit test files.

Move the `core/test.py` file to `tests' folder.

Modify the folder path to import modules in `tests/test.py' file.
Modify folder path to import modules

- All import of modules is now done from the project root folder and
  hence reflects `pysymoro` in the import statement.
Update `.gitignore`
Modify to use `os.path.join()` to join folders