Don't update Composer on each buld
minor #111 Don't update Composer on each buld (aik099)

This PR was merged into the 2.0-dev branch.

Discussion
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Don't update Composer on each buld

Currently at least 1 of builds in build matrix fails because of `composer self-update` command in the `.travis.yml`. See https://travis-ci.org/fabpot/Sami/jobs/30440724

I've removed it since I haven't witnessed a case, that even month old `composer.phar` has created problems during a build.

Commits
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3aaf100 Don't update Composer on each buld