Avoid interpreting path as route

[tt]

I was trying to upgrade Bypass in a project but ran into the issue reported in #122.

Bypass will currently interpret a path as a route by using Plug.Router.Utils.build_path_match to split it into path segments.

The simplest demonstration of that is by using /resources/:resource as both route pattern and path. The resource parameter is then supposed to be :resource but as both are interpreted as route, the parameter ends up being {:resource, [], nil}. This may not be a problem based on whether the expectation relies on this parameter.

However, another scenario is if your path contains multiple colons, e.g. /resources/a:b:c. With Bypass' current dependency on Plug 1.10.4, this fails with the following exception:

     ** (Plug.Router.InvalidSpecError) :identifier in routes must be made of letters, numbers and underscores
         (plug 1.10.4) lib/plug/router/utils.ex:209: Plug.Router.Utils.binary_to_identifier/2
         (plug 1.10.4) lib/plug/router/utils.ex:166: Plug.Router.Utils.segment_match/3
         (plug 1.10.4) lib/plug/router/utils.ex:131: Plug.Router.Utils.build_path_match/4
         (bypass 2.1.0) lib/bypass/instance.ex:300: Bypass.Instance.route_info/3
         (bypass 2.1.0) lib/bypass/instance.ex:162: Bypass.Instance.do_handle_call/3
         (stdlib 6.2) gen_server.erl:2381: :gen_server.try_handle_call/4
         (stdlib 6.2) gen_server.erl:2410: :gen_server.handle_msg/6
         (stdlib 6.2) proc_lib.erl:329: :proc_lib.init_p_do_apply/3
     Last message (from #PID<0.10094.0>): {:get_route, "POST", "/resources/a:b:c"}

Upgrading Plug to its latest release, version 1.16.1, changes the error but still fails:

     ** (Plug.Router.InvalidSpecError) only one dynamic entry (:var or *glob) per path segment is allowed, got: "a:b:c"
         (plug 1.16.1) lib/plug/router/utils.ex:236: Plug.Router.Utils.build_path_clause/7
         (plug 1.16.1) lib/plug/router/utils.ex:142: Plug.Router.Utils.build_path_clause/3
         (plug 1.16.1) lib/plug/router/utils.ex:84: Plug.Router.Utils.build_path_match/2
         (bypass 2.1.0) lib/bypass/instance.ex:300: Bypass.Instance.route_info/3
         (bypass 2.1.0) lib/bypass/instance.ex:162: Bypass.Instance.do_handle_call/3
         (stdlib 6.2) gen_server.erl:2381: :gen_server.try_handle_call/4
         (stdlib 6.2) gen_server.erl:2410: :gen_server.handle_msg/6
         (stdlib 6.2) proc_lib.erl:329: :proc_lib.init_p_do_apply/3
     Last message (from #PID<0.903.0>): {:get_route, "POST", "/resources/a:b:c"}

Switching the implementation to use Plug.Router.Utils.split resolves the issue.