Add code style and code organization

[splincode]

1. Add tslint.json
2. Add travis CI
3. Add codecoverage
4. Add contributing.md+ precommit hooks
5. Add changelog generator

[obenjiro]

Should we close this issue?

[splincode]

There are 3 more things left to do

3. Add codecoverage
4. Add contributing.md+ precommit hooks
5. Add changelog generator

[tplk]

To generate reasonable changelogs it's better to enforce commit message format.
I'd suggest conventional-changelog which is based on angular's commit msg format.

[tplk]

@splincode also you should update issue message to represent progress.

~1. Add tslint.json~
~2. Add travis CI~
3. Add codecoverage
4. Add contributing.md+ precommit hooks
5. Add changelog generator