Don't quote shell commands
Let Travis run 'mvn install' for us

By default [1], Travis will run 'mvn install -DskipTests=true' for
Maven-based projects. This will build and install all required
dependencies (including our own artifacts).

[1] http://about.travis-ci.org/docs/user/languages/java/#Dependency-Management
Run integration tests only
Attach all target platform definitions
The matrix build

Run integration tests against all three available target platforms:
- Eclipse Helios
- Eclipse Indigo
- Eclipse Juno
Use Anthony Dahanne's P2 repository for Helios-based TP
Update ADT feature's version
Include DDMS, Hierarchy Viewer and Traceview features into Helios TP
Drop running integration tests against Eclipse Helios

Eclipse Helios has been released in 2010 and its TP definition is
broken anyway.

[1] http://eclipse.org/helios/
Merge pull request #160 from manandbytes/travis-ci

Run integration tests for all supported target platforms