Update security.md

Hi Guys 
I was reading through this guide last night and noticed a small mistake, would be great if you could update it. 
I changed the word 'building' to 'build' in line 20. 
"Web application frameworks are made to help developers building web applications"
A tiny grammatical fix

[ci skip]
Fixes problem with replacing has_one association record with itself
Merge pull request #12834 from dredozubov/has_one_association_replacement

Fixes problem with replacing has_one association record with itself
Load test fixtures where data are needed

Without this, some tests here were not actually testing anything.
Avoid sorting an Array including objects from different Classes

addresses "ArgumentError: comparison of VerySpecialComment with SpecialComment failed" in ActiveRecord::DelegationRelationTest#test_#sort!_delegation_is_deprecated
tidy Active Record CHANGELOG. [ci skip].
Fixed typo in migrations guide

Product model name was pluralized in example in migrations guide.
[ci skip]
Merge pull request #12847 from jipe/master

Fixed typo in migrations guide [ci skip]
Do not count "SHOW CREATE TABLE" queries when testing against mysql
test cases to describe the MySQL boolean behavior.
Unifies mysql and mysql2 casting of booleans.
Merge pull request #12425 from senny/mysql_booleans

Unify boolean quoting for Mysql- and Mysql2Adapter.
Merge pull request #12815 from Adam89/patch-1

Update security.md [ci skip]
Prevent the counter cache from being decremented twice

when destroying a record on a has_many :through association.
:destroy method has own counter_cache callbacks.
documentation updated for Hashes [ci skip]
Merge pull request #12748 from dm1try/fix_counter_cache_for_through_association

Fixes #11079, prevent the counter cache from being decremented twice when destroying a record on a has_many :through association
Merge pull request #12854 from kuldeepaggarwal/f-indentation

methods and outputs indented [ci skip]
updated documentation for Integer
Allow Pathnames to be added to eager load paths