Fix docker build error on gem install sass (#26)

Added apt-get install build-essential ruby ruby-dev ruby-ffi to fix error on docker build, error output was gem install sass fail. Update to ENV version constants.

update ionic (#25)

update ionic and node LTS (#24)

update ionic, node LTS and gradle (#23)

update ionic cli and nodejs (#22)

update ionic to 3.15.1 (#21)

ionic 3.15.0 and nodejs 8.8.0 (#20)

update ionic to 3.14.0 (#19)

update to ionic 3.13.1 (#16)

Update Ionic (#15)

- Ionic to 3.13.0
- Node to 8.6.0
- Gradle to 4.2.1