refactor the naming within plugin new generator

Having a method called `full?`, which checks on :full and :mountable
is very confusing. I renamed `full?` to `engine?` and created a `full?`
method that only checks the `:full` option
change spy of  after invoked controller action. because ruby-2.0.0 waned unused variables
Eager loading made to use relation's in_clause_length instead of host's one (fixes #8474)
Install binstubs by default
Detect rbenv and update the shebang
Add --no-html to scaffold generator
Forgot to check in railties fixture for binstubs
Ignore /bin on new apps
adds kindlerb to the :doc bundle group for guides generation
Fixes for PR [#8267]
* Fix Migration#reversible by not using `transaction`.

* Adapt mysql adapter to updated api for remove_column

* Update test after aedcd683684d08eaf30623a4b48ce31a31426372
Fix syntax error in controller template
Fix spacing regression in scaffold generator
Merge pull request #8588 from marcandre/fix_reversible

Fix Migration#reversible by not using `transaction`.
Remove warning of intance variable not initialized
remove duplication from Rails::Application docs
Merge pull request #8593 from shime/master

another little documentation fix
Explicit options should have precedence over railsrc on the `rails new`
command

Closes #8545
we're not supporting SQLite 2
Merge pull request #8594 from amatsuda/rm_sqlite2

I don't think we're supporting SQLite 2
"warning: ambiguous first argument; put parentheses or even spaces"