Check installation errors

In case of error the command and status code will be shown.
If --install-error-action=abort the installation will be aborted.
Proper flushing of install logs
Fix typo in message

There was a typo in a message in the Windows installer script.
Merge pull request #442 from fernandoacorreia/windows-php-typo

Fix typo in message
Merge pull request #428 from fernandoacorreia/install-error-checking

Check installation errors
bumped up Selmer version
Merge pull request #443 from yogthos/patch-1

bumped up Selmer version
Merge branch 'master' of https://github.com/TechEmpower/FrameworkBenchmarks