* 3.1: (30 commits)
Fix merge
[HttpFoundation] Use UPSERT for sessions stored in PgSql >= 9.5
[Console] fixed PHPDoc
[Cache] Fix double fetch in ProxyAdapter
[travis] HHVM 3.12 LTS
Fix feature detection for IE
[Form] Fixed collapsed choice attributes
[Console] added explanation of messages usage in a progress bar
force enabling the external XML entity loaders
[Yaml] properly count skipped comment lines
[WebProfilerBundle] Fix invalid CSS style
Added progressive jpeg to mime types guesser
[Yaml] Fix wrong line number when comments are inserted in the middle of a block.
Fixed singular of committee
Fixed singular of committee
Do not inject web debug toolbar on attachments
Fixed issue with legacy client initialization
[FrameworkBundle] Remove unused variable
bumped Symfony version to 3.0.8
updated VERSION for 3.0.7
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