Synchronize `rspec spec` and `rake spec` output

By removing the `rake spec` short circuiting the output between
invocation methods matches more closely.

Fixes rspec/rspec-core#812
Adding trim option to ERB, closes #840
Adding test to make sure we can parse ERB format if trimming dash is used
Replacing condition to true
Removing SyntaxError expectation
Fix sandboxing of rspec-core's own specs.

Because rspec-core dog-foods itself, rspec-core's spec suite has
examples that define example groups and examples and run them. The
usual lifetime of an RSpec::Mocks::Proxy is for one example
(the proxy cache gets cleared between each example), but since the
specs in rspec-core's suite sometimes create test doubles and pass
them to examples a spec defines and runs, the test double's proxy
must live beyond the inner example: it must live for the scope
of wherever it got defined. Here we implement the necessary semantics
for rspec-core's specs:

- #verify_all and #reset_all affect only mocks that were created
 within the current scope.
- Mock proxies live for the duration of the scope in which they are
 created.

Thus, mock proxies created in an inner example live for only that
example, but mock proxies created in an outer example can be used
in an inner example but will only be reset/verified when the outer
example completes.

These changes were needed due to the recent refactoring in rspec-mocks
which changed what held a reference to the mock proxy (a proxy cache
rather than an instance variable on the mocked object) and the
lifecycle of those proxies (cleared between each example rather
than persisted for the rest of the process).
Update Changelog for #846.

[ci skip]
added failing spec for calling #let w/o a block
Give a useful error when let or subject called without a block.

This is done by nil chcking the block in let before using it.

Signed-off-by: Sam Phippen <samphippen@googlemail.com>
Changelog entry for new subject/let error messages

Signed-off-by: Sam Phippen <samphippen@googlemail.com>
Unify "run everything" cukes and clarify usage

This collapses the descriptions of both former
run_everything_when_everything_filtered features. Additionally it adds
a scenario showing that the setting only applies to inclusion filters,
not exclusion filters.
Update the cucumber for configuration files for .rspec-local

this is so we get some docs on relish for this.

Signed-off-by: Sam Phippen <samphippen@googlemail.com>