Written a failing feature to describe how fuzzy collection matching works.
Should be able to do fuzzy matching against arrays using include?(some_matcher) or include?(array_of_matchers).

I've deliberately only implemented fuzzy matching support for arrays right now, it might make sense
to extend support to hashes though.
Slight tweak to the cucumber feature to get it passing.
Favour duck-type checks over class checks
Started to add some integration specs to show the interaction between include()
matcher support and the built-in matchers.
It helps to use the matcher you are testing
Switch to new expect syntax.
Cleanup whitespace.
When composing matchers with `include` it should not be diffable.

Otherwise, we get ridiculous output like:

     Failure/Error: expect(['foo', 'bar', 'baz']).to include(string_containing_string("abc"))
       expected ["foo", "bar", "baz"] to include a string containing 'abc'
       Diff:
       @@ -1,30 +1,2 @@
       -[#<RSpec::Matchers::DSL::Matcher:0x007fb244f536f8
       -  @actual="baz",
       -  @declarations=
       -   #<Proc:0x007fb244c1a5e0@/Users/myron/code/rspec-dev/repos/rspec-expectations/spec/rspec/matchers/include_spec.rb:390>,
       -  @diffable=false,
       -  @expected=["abc"],
       -  @expected_exception=nil,
       -  @match_block=
       -   #<Proc:0x007fb244f52b18@/Users/myron/code/rspec-dev/repos/rspec-expectations/spec/rspec/matchers/include_spec.rb:391>,
       -  @match_for_should_not_block=nil,
       -  @matcher_execution_context=
       -   #<RSpec::Core::ExampleGroup::Nested_89::Nested_1:0x007fb244f53dd8
       -    @example=
       -     #<RSpec::Core::Example:0x007fb244c378e8
       -      @around_each_hooks=nil,
       -      @example_block=nil,
       -      @example_group_class=nil,
       -      @example_group_instance=nil,
       -      @exception=nil,
       -      @metadata=nil,
       -      @options=nil,
       -      @pending_declared_in_example=nil>,
       -    @matcher_execution_context=
       -     #<RSpec::Core::ExampleGroup::Nested_89::Nested_1:0x007fb244f53dd8 ...>>,
       -  @messages=
       -   {:description=>
       -     #<Proc:0x007fb244f52af0@/Users/myron/code/rspec-dev/repos/rspec-expectations/spec/rspec/matchers/include_spec.rb:395>},
       -  @name=:string_containing_string,
       -  @rescued_exception=nil>]
       +["foo", "bar", "baz"]
Shorten verbose matcher name.

string_containing_string => a_string_containing
Add specs for `expect().not_to include(matcher, matcher)`.
Add changelog entry for #85.