Cleanup docs for route matching.

Documents:
  - mixing of named (token) matching and wildcard matching. Moved (and
    corrected) route chaining example. (Ref: #729)
  - megasplat (**) as part of wildcard matching (duplicate content from
    splat keyword).
  - Note support for named capture groups in section about regex routes.
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Merge branch 'docs/route_params_and_splats'
Update test skeleton to use to_app
Change test skeleton to OO style Plack::Test
spacing
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Merge branch 'pr/update_test_skeleton_to_app'
Reworked tests to use Plack::Test
Reworked test to use Plack::Test
Added test for returned content
Deleted t/server_standalone based on #636
Changed Dancer2->runner->psgi_app to Dancer2->psgi_app
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Merge branch 'pr/test_rework_plack_test'
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Merge branch 'doc/testing'
v0.154000

    [ BUG FIXES ]
    * GH #744: Serialize anything, not just references. (Sawyer X)
    * GH #744: Serialize regardless of content_type of serializer. (Sawyer X)
    * GH #764: Catch template render errors. (Russell Jenkins, Steven Humphrey)
    * Calling uri_for(undef) doesn't crash. (Sawyer X)
    * GH #732: Correct name for 403 (Forbidden, not Unauthorized).
      (Theo van Hoesel, Sawyer X, Mickey Nasriachi, Omar M. Othman)
    * GH #753: Syntax of parameterized types. (Russell Jenkins)
    * GH #734: Failing tests on Windows. (Russell Jenkins, Sawyer X)

    [ ENHANCEMENTS ]
    * GH #664, #684, #715: Handler::File replaced for static files with
      Plack::Middleware::Static, allowing files to be served *before* routes.
      This means hooks do not apply to static files anymore!
      (Russell Jenkins, DavsX)
    * Engines now have "logger" attribute to log errors. It sends the
      Dancer2::Logger:: object, if one exists. (Sawyer X)
    * Serializers do not need to implement "loaded" method. (Sawyer X)
    * GH #733: In core: response_xxx removed in favor of generic
      standard_response. (Sawyer X, Mickey Nasriachi, Omar M. Othman)
    * GH #514, #642, #729: Allow mixing named params, splat, and
      megasplat. (Russell Jenkins, Johan Spade, Dávid Kovács)
    * GH #596: no_server_tokens works, as well as DANCER_NO_SERVER_TOKENS.
      (Omar M. Othman, Sawyer X, Mickey Nasriachi)
    * GH #639: Validate engine types in configuration.
      (Sawyer X, Omar M. Othman, Mickey Nasriachi, Russell Jenkins)
    * GH #663, #741: Remove "accept_type" attribute and other references.
      (Mickey Nasriachi, Theo van Hoesel)
    * GH #748: Provide forwarded_host, forwarded_protocol. (Sawyer X)
    * GH #748: Do not provide a default env, require env for a request.
      (Sawyer X)
    * GH #742: Update test skeleton to use to_app. (Dávid Kovács)
    * GH #636: Use Plack::Test in more tests. (Dávid Kovács)

    [ DOCUMENTATION ]
    * GH #656: Dancer2::Manual::Testing as a guide for testing Dancer2
      applications. (Sawyer X)
    * Improved documentation of route matching. (Russell Jenkins)
    * Migration document update relating to enhancements.
      (Sawyer X, Mickey Nasriachi)
    * GH #731: Document changes in session.
      (racke, Sawyer X, Mickey Nasriachi, Omar M. Othman)
    * Document "id" attribute in Request object. (Sawyer X)
    * Correct Cookbook examples on command line scripts. (Sawyer X)
Merge branch 'release/0.154000'
Remove unnecessary hack for handling static files with middleware:

We no longer need this workaround because now we serve static files
using the middleware instead.