[2.3.2] Release readiness

- Updated version constant
- Created changelog
- Updated README
Merge branch 'releases/2.3.2'

2.3.2 release readiness
Bump to next dev version

- 2.3.3dev
Merge branch 'version/bump'

Bump to 2.3.3dev
fix and failing testcase for custom barcode adapters in barcode object construtor
update invalid adapter exception message
Merge pull request #6576 from fabiocarneiro/hotfix-custom-barcode-validator

hotfix custom barcode adapter wasn't being set to options.
[#6576] do not use short array syntax

- as we still support 5.3.
[#6576] CS fixes (trailing whitespace)
Merge branch 'hotfix/6576'

Close #6576
fix Ldap converter serialize test

Starting from PHP versions 5.4.30, 5.5.14 and 5.6.0beta4, the serialized
representation of a DateTime includes fractional seconds.
The data provider must check the PHP version and provide a correct
serialized representation of the DateTime object.

refs #6468
fix Atom tests with fractional seconds in dates

the DateTime object is correctly created in Extension\Atom\Entry#L173,
but the tests created the comparison DateTime with the wrong format (ISO8601)
and the wrong datetime string (did not include the fractional seconds)
remove conditional in dataProvider and replace with serialized object
Use file_exists to check for an uploaded file.

It turns out that stream_resolve_include_path doesn't work for a default
Windows install where upload_tmp_dir is set to C:\Windows\Temp. I'm
unclear if this is intended PHP behaviour or not, but the upload file
validator should not be checking for a file of the same name on the
include path regardless.
Use is_file() rather than file_exists().
Allow running php-cs-fixer in parallel

A recent change in php-cs-fixer has led to massive performance issues, leading
to timeouts of ZF2 builds. This change is a band-aid, and does the following:

- Alters the php-cs-fixer configuration to remove the lines that excluded
  top-level paths, and added paths to test. This means you cannot just run
  "php-cs-fixer" in the root anymore; you **must** pass a directory in which to
  run the checks.
- Alters the Travis-CI configuration to list the directories in which to run
  php-cs-fixer and pass them to the `parallel` command.

The changes ensure that output will occur periodically. The checks run
_somewhat_ faster, though the performance improvement is certainly less than
50%.
Switched to known good revision of php-cs-fixer

- Determined from last build that did not have CS errors flagged.
Updated php-cs-fixer rules

- Path restrictions must be specified differently when you pass the path to a
  component via the CLI as an argument to php-cs-fixer; they become relative to
  the argument, not the project root.
Re-instated two notPath() rules
Merge branch 'hotfix/#6671-fixed-parallelized-cs-checks'

Close #6671