report buildtime data to keen io
add comment
fix typo in argument example string
log repo name
log travis repo slug
replace property 'id' by 'build'
add KEEN_PROJECT_ID
add KEEN_WRITE_KEY, close #1

use KEEN_MASTER_KEY as WKEEN_WRITE_KEY. It is not as long, so you don't
run into SSL limits when encrypting its value, see issue #1.