avoid using alias in generators

Ruby's alias produces public methods, causing a spurious Thor task
to be created.  For example, this is the reason MigrationGenerator
currently has two tasks:

    > ActiveRecord::Generators::MigrationGenerator.all_tasks.keys
    => ["singular_name", "create_migration_file"]

singular_name was meant to be an attribute, not a task.  Because it's
public, it gets called as a task every time the generator is invoked.

The fix is to ensure all generator methods have the correct
visibility.
Fixed `columns_for_distinct` of postgresql adapter
Added partial days support to `DateTime`'s `advance` method.

You can now add partial days (e.g. 2.5.days) to `DateTime` with the advance method.
This was acheived by mimicing the `advance` implementation in `Time`.
Fixed changelog
Added documentation for the :param option for resourceful routing
Swallow bundler exceptions when running tests

Let's avoid useless output when testing stuff related to Bundler.
Remove unnecessary include for integration tests.
:scissors:
Fixed a problem where `sum`, `size`, `average`, `minimum` and `maximum` used
with a grouping was not returning a Hash.
WIP: pass existing joins to construct_join_dependency
Rename Posts to Articles in Guides, continuation of 2d446e77 / #13774 [ci skip]
Merge pull request #15215 from JohnKellyFerguson/rename-posts-to-articles

Documentation: Rename Posts to Articles
Update CHANGELOG.md

Most recent change should be moved to the top
Merge pull request #14803 from kuldeepaggarwal/null_relation_sum_fix

Fixed a problem where `sum` used with a `group` was not returning a Hash.
Form full URI as string to be parsed in Rack::Test.

There are performance gains to be made by avoiding URI setter methods.
Merge pull request #15101 from tgxworld/improve_performance_of_building_uri

Form full URI as string to be parsed in Rack::Test.
pg test, remove unused code.
Do not gsub non ASCII characters in header anchor.
pg test, extract network address type tests into separate file.
pg test, move timestamp tests over to `postgresql/timestamp_test.rb`.