Update README
Update CHANGELOG for Release 7.4.0
Install unixodbc for Erlang packages.

This enables Erlang to be compilex with built-in ODBC support.

Fixes travis-ci/travis-ci#2254
Merge pull request #308 from travis-ci/gc-changelog-releases

Update CHANGELOG for Release 7.4.0
Merge pull request #292 from travis-ci/readme

Update README
Merge pull request #310 from travis-ci/mm-erlang-unixodbc

Install unixodbc for Erlang packages
Don't preinstall old versions of Scala and sbt

Note: sbt 0.13.1 is still pre-installed as it is the default version of
the current sbt-extras launcher script.
Add Erlang/ODBC change to changes.
Merge branch 'master' into mm-change-git-ppa
Update changes.