Fix/schematics ng add scss

[aqupriyanka]

closes #7

What's included?

Refactor ng-add @covalent/core so that

it doesn't add theme.scss anymore
put what is in theme.scss into bottom of styles.scss and remove theme.scss

Test Steps

• Navigate to scripts directory
• Run ./test-schematics.sh : this is the script to test this entire feature locally
• this will create a folder testxyz in tmp directory.
• verify that teme.scss file should not be pressent in the testxyz/src folder.
• verfilt styles.scss should include theme.scss