Removes #to_str implememtation from test_double

Having test_double implement to_str makes the Ruby
runtime coerce it to a string whenever needed and
this isn't the intended behavior for this object.
This behavior led to issue #567 as Ruby will try
to coerce the exception object into string when raising
(here https://github.com/ruby/ruby/blob/191b373d26a48058bcc8955bf3afe426f60eaaea/eval.c#L678 )
an exception and since test_double does implement to_str
it succeded and raises that instead of failing with the
correct 'this is not an exception object' error.

This fixes #567 by providing a better error message
in it's case.
Ignoring `raise double()` specs for ruby 1.9.2

This ignores specs that check for the removal of
`to_str` from Ruby 1.9.2 as they won't work there
due to the Ruby runtime calling `to_str` on a double
without checking if the double implements `to_str`.
Move enhancements above bug fixes in changelog.

[ci skip]
Grammar in Changelog.

[ci-skip]
Merge pull request #577 from mauricio/issue-567

Removes #to_str implementation from test_double
Add changelog entry for #577.

[ci skip]
Add release notes from 2.99.0.beta2.

[ci skip]
Update changelog for 3.0.0.beta2 release. [ci skip]
Release 3.0.0.beta2
Prepare changelog for 3.0.0.rc1 development.
Fix any instance mark_invoked blocks not being cleared properly.

This issue was caused by the order that mocks were torn down in
space.rb. This happened because (in order):

1. Each mock proxy is verified
2. Each any_instance recorder is verified

any_instance verification also currently holds the code for tearing down
any_instance recorders also.

If any mock proxy through an exception whilst it was being verified then
none of the any_instance recorders were verified (which makes sense as
verification of mocks has already failed).

This patch adds a teardown of the any_instance_recorders in reset_all to
RSpec::Mocks::Space
Fixup any_instance specs to call space#reset_all
Add a changelog entry for #580
Cleanup any-instance specs
Merge pull request #580 from rspec/any-instance-lifecycle-management

Fix any instance mark_invoked blocks not being cleared properly.
"full changelog" => "Full Changelog"
Remove obselete `Upgrade.md` file.
Add 2.14.6 release notes.

[ci skip]
Log a warning when methods are reset on a frozen object
Fixup specs for frozen mock object resets