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"
Array#split preserving the calling array
Array#in_groups: documentation updated
Merge pull request #12839 from kuldeepaggarwal/array_split

Array#split preserving the calling array
Fix missing line and shadow on static error pages [ci skip]
Merge pull request #12841 from kuldeepaggarwal/in-group-documentation

Array#in_groups: documentation updated [ci skip]
autoload ChangeColumnDefinition (Fixes #12835)
Speed up Array#split
Ruby 2.0.0p247
Rehearsal ---------------------------------------
old  10.670000   0.150000  10.820000 ( 10.822651)
new   8.520000   0.050000   8.570000 (  8.571825)
----------------------------- total: 19.390000sec

          user     system      total        real
old  10.620000   0.170000  10.790000 ( 10.790409)
new   8.570000   0.110000   8.680000 (  8.686051)
Merge pull request #12842 from kuldeepaggarwal/array_split

Speed up Array#split when block is passed
Merge pull request #12843 from DeltaKilo/css_fix

Fix missing line and shadow on static error pages [ci skip]
Merge pull request #12844 from akalyaev/bugfix/12835-autoload-change-column-definition

autoload ChangeColumnDefinition (Fixes #12835)
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