don't warn about sudo on windows

fixes #2984
Demonstrate that call to bundle update fails in multi-platform spec

For this spec to make sense, the call should succeed, since otherwise
the cache update never runs and the spec will pass trivially.
Ensure Gemspec.lock and Gemfile match in multi-platform cache spec

The activerecord 2.3.3 gem needs activesupport 2.3.2, which was not
included in the Gemfile.lock or cache. This caused bundle update to
fail. This change simplifies the set of needed gems, thereby returning
to an older version of this spec. By adding the mri platforms to the
block for 'rack' we keep the check for allowed platforms.
Make describe block description match tested method
Move test of valid platforms out of multi-platform spec
Use Ruby 1.8-compatible hash syntax
Merge pull request #3034 from mvz/ensure-success

Ensure `bundle update` runs succesfully in specs of multi-platform cache behavior
add slack notifications
add gittip badge
Fix use of deprecated failure_message_should

- Replaced with failure_message
Merge pull request #3043 from prathamesh-sonpatki/fix-deprecation-warning-for-failure-message-should

Fix use of deprecated failure_message_should

[ci skip]
Extract standalone path expansion to do it only once
Merge pull request #3044 from Juanxo/extract-standalone-path-expansion

Extract standalone path expansion to do it only once
fix the rspec rake task on 1.8.7
check rspec version while running specs
add travis results to slack #general room

[ci skip]
Update Travis config w/correct rbx version
Merge pull request #3047 from jc00ke/master

Update Travis config w/correct rbx version
Don't include configured source credentials in lockfile.
Add `bundle viz --without` to exclude gem groups from resulting graph.

This commit introduces a `--without` flag (similar to the flag on the
`install` subcommand) which will drop the inclusion of these gems from
the graph.

The ability to exclude gem groups from the graph is very useful when
trying to visualize or understand the runtime dependencies of a
particular RubyGem or project, minus any development or test related
libraries.

Previously the process of reproducing this behavior was a manual
process:

* Inspect the project's Gemfile and comment/remove any gems that are not
  runtime dependencies. Typically these gems would be in `:test` or
  `:development` groups.
* Inspect the project's gemspec (if it exists) and comment/remove any
  gems that are not runtime dependencies.

Now it is as simple as:

    bundle viz --without=test development