Fix article for generator name

Use 'some' instead of 'a/an'.
active_record: Quote numeric values compared to string columns.
Skip schema dumper extensions test if connection does not support it

Travis failed because the postgresql version installed there does not
support extensions, so we just need to skip this for now.
Merge pull request #9207 from dylanahsmith/mysql-quote-numeric

active_record: Quote numeric values compared to string columns.
Merge pull request #9185 from tricknotes/fix-article-for-generator-name

Fix article for generator name
Change behaviour with empty hash in where clause
Merge pull request #9220 from robertomiranda/where-with-empty-hash

Active Record: Change behaviour with empty hash in where clause
Change behaviour with empty array in where clause
Merge pull request #9216 from robertomiranda/where-with-empty-array

Activer Record:  Change behaviour with empty array in where clause
Improve changelog entries in AR

Describe better the changes related to raising errors with empty
array/hash values in where clauses.

[ci skip]
Fix #9168 Initialize NullCookieJar with all options needed for KeyGenerator
Reverting 16f6f25 (Change behaviour with empty array in where clause)
Bump rack dependency to 1.5.2
Merge pull request #9196 from AndreyChernyh/fix-cookies-with-null-session

Fix #9168 Initialize NullCookieJar with all options needed for KeyGenerator
We don't need a CHANGELOG entry for an issue of something that was not released yet
Reverting e170014113 (Change behaviour with empty hash in where clause)
Add missing require to AP
Use IN operator like arel for empty hash in where clause
Merge pull request #9232 from robertomiranda/where-with-empty-hash

Use IN operator like Arel for empty hash in where clause
Update activerecord/CHANGELOG.md