Send test specific `Accept` headers
Fix #429: JRuby installation failing

At the time of writing, this will install Maven 3.0.4 on an Ubuntu 12.04 system. Tests indicate that build does not require version 3.0.5, and the official repositories should update as new versions are released.
Fix #431: Composer installation error

By moving Leiningen installation to the top, the bin directory will be created before Composer is installed.
Fix #430: vertx installation error

Download link updated.
Fix  #432: Siena installation error

Tests show that there is no error if the answer is piped from `yes`.
Fix error in __install_client_software

Fixes to run the command in the repository's root directory instead of in 'installs'. Fixes error introduced by commit 7d3f0144ecd7dc5147dca704459f83081272c7fd.
Installer: improve debug messages

grep '^INSTALL' will show the commands and errors without noise.
Standardize commenting style for consistency
Merge pull request #447 from fernandoacorreia/facorreia-installer-fixes

Installer fixes
Merge pull request #437 from kppullin/test_aware_accept_headers

Send test specific `Accept` headers