Closes #15024.

These operations happen before instances are created.
The current behavior is misleading and can result in broken behavior.

Fix broken proc syntax for 1.9.3

This lets us avoid

1. A slow call to Hash#slice
2. An is_a? test
3. Extra hash allocations (from slice)
4. String allocations

etc.

avoids extra hash allocations on each call

this is due to:

  https://bugs.ruby-lang.org/issues/5994

Documentation, add examples of using an Enum scope [ci skip]

When scanning the Enum API page I found it easy to miss that scopes are generated.  Adding an example clarifies use and has more... *pop*...

Only need MINOR version level to test Ruby 2.1.x on Travis

cc http://blog.travis-ci.com/2014-04-28-upcoming-build-environment-updates/

Reverts dirty track restore on transactions rollback

do not test internals

We are reverting these commits, because there are other caveats related
to dirty attributes not being restored when a transaction is rollback.
For instance, nested transactions cannot proper restore the dirty
attributes state after a rollback.

At the moment, the dirty attributes are scoped by the transaction.
When we call `.save` on a record, the dirty attributes will be reset even
if the transaction gets rollback.

[related #13166]
[related #15018]
[related #15016]
[closes #15019]

This reverts commits
* bab48f0a
  * b0fa7cf3.
* 73fb39b6
  * 37c23892.
  * 8d8d4f15

Revert "Merge pull request #13166 from bogdan/transaction-magic"

Current docs are wrong. Does not accept strftime inputs.

Use ruby 2.1.2 on travis

Change 'a' to 'an' [ci skip]

[ci skip] Minor improvements on routing.md.

I wanted the middle model to be anonymous, but we have to give it a name
for marshal support. :'(

This test was inspired by #14866. That PR would break this
functionality and we should make sure we notice that in the future.

Habtm relation size calculation fix. Fixes #14913, Fixes #14914.

This resulted in some unrelated errors on Traivs:

  1) Error:
PostgresqlUUIDTest#test_treat_blank_uuid_as_nil:
ActiveRecord::StatementInvalid: PG::UndefinedColumn: ERROR:  column "thingy" of relation "uuid_data_type" does not exist
LINE 1: INSERT INTO "uuid_data_type" ("thingy") VALUES ($1) RETURNIN...
                                      ^
: INSERT INTO "uuid_data_type" ("thingy") VALUES ($1) RETURNING "id"

/cc @zuhao

HABTM should fall back to using the normal CollectionAssociation's size calculation if the collection is not cached or loaded.

This addresses both #14913 and #14914 for master.