Update changelog.txt
Update changelog.txt

- Add security section
- Add Travis CI

PhrozenByte/Pico,lukasz-jakub-adamczuk/tech-jump-guide,picocms/Pico,dav-m85/Pico,TakamiChie/Pico,picocms/Pico,smcdougall/Pico,lukasz-jakub-adamczuk/tech-jump-guide,theshka/Pico,ondrejd/Pico,theshka/Pico,fabianacero/fabianacerog,TakamiChie/Pico,ondrejd/Pico,lukasz-jakub-adamczuk/tech-jump-guide,PhrozenByte/Pico,ondrejd/Pico,TakamiChie/Pico,PhrozenByte/Pico,smcdougall/Pico,TakamiChie/Pico,dav-m85/Pico,picocms/Pico,fabianacero/fabianacerog,fabianacero/fabianacerog,theshka/Pico,dav-m85/Pico,smcdougall/Pico