Added mesos-scala-api to api-client-libraries.md.
Added mesos-scala-api to api-client-libraries.md.

Added a link to a 3rd party Scala API library to documentation.

This closes #143

Aman-Jain-14/customizedMesos,yuquanshan/customizedMesos,Gilbert88/mesos,asamerh4/mesos,asamerh4/mesos,asamerh4/mesos,Aman-Jain-14/customizedMesos,jpeach/mesos,Aman-Jain-14/customizedMesos,reneploetz/mesos,Gilbert88/mesos,reneploetz/mesos,andschwa/mesos,verizonlabs/mesos,kaysoky/mesos,craimbert/mesos,reneploetz/mesos,yuquanshan/customizedMesos,dforsyth/mesos,kaysoky/mesos,jpeach/mesos,kaysoky/mesos,Gilbert88/mesos,Aman-Jain-14/customizedMesos,jpeach/mesos,Aman-Jain-14/customizedMesos,gsantovena/mesos,jpeach/mesos,gsantovena/mesos,yuquanshan/customizedMesos,abudnik/mesos,verizonlabs/mesos,Gilbert88/mesos,chhsia0/mesos,jpeach/mesos,reneploetz/mesos,yuquanshan/customizedMesos,abudnik/mesos,Gilbert88/mesos,neilconway/mesos,abudnik/mesos,kaysoky/mesos,neilconway/mesos,neilconway/mesos,zmalik/mesos,verizonlabs/mesos,craimbert/mesos,zmalik/mesos,chhsia0/mesos,yuquanshan/customizedMesos,zmalik/mesos,gsantovena/mesos,reneploetz/mesos,neilconway/mesos,yuquanshan/customizedMesos,andschwa/mesos,craimbert/mesos,craimbert/mesos,jpeach/mesos,chhsia0/mesos,neilconway/mesos,reneploetz/mesos,zmalik/mesos,craimbert/mesos,dforsyth/mesos,chhsia0/mesos,kaysoky/mesos,verizonlabs/mesos,craimbert/mesos,reneploetz/mesos,neilconway/mesos,Gilbert88/mesos,neilconway/mesos,andschwa/mesos,verizonlabs/mesos,dforsyth/mesos,Aman-Jain-14/customizedMesos,Aman-Jain-14/customizedMesos,abudnik/mesos,jpeach/mesos,kaysoky/mesos,abudnik/mesos,zmalik/mesos,Gilbert88/mesos,zmalik/mesos,asamerh4/mesos,gsantovena/mesos,chhsia0/mesos,chhsia0/mesos,dforsyth/mesos,craimbert/mesos,asamerh4/mesos,asamerh4/mesos,dforsyth/mesos,zmalik/mesos,andschwa/mesos,gsantovena/mesos,dforsyth/mesos,asamerh4/mesos,andschwa/mesos,verizonlabs/mesos,abudnik/mesos,andschwa/mesos,yuquanshan/customizedMesos,verizonlabs/mesos,gsantovena/mesos,dforsyth/mesos,chhsia0/mesos,kaysoky/mesos,gsantovena/mesos,abudnik/mesos,andschwa/mesos