add some mock tests for http downloads
allow using LWP::UserAgent as HTTP protocol_class

1) Use eval to load the protocol_class requested
2) Add check_http_response to check for HTTP::Response objects

This also adds support for file:// URLs, to allow LWP to be tested
directly.
Test::More 0.94 is required for subtest
include headers along with content for check_http_response
Merge branch 'lwp' of github.com:plicease/Alien-Base into plicease/lwp

Conflicts:
	lib/Alien/Base/ModuleBuild/Repository/HTTP.pm

This merges the changes between #24 and #55. See #56.

Merging of [commit](https://github.com/plicease/Alien-Base/commit/a15536c804b9738ae3d45cd9a23ca427855c8927)
by @plicease which adds header support for both LWP and HTTP::Tiny. This
is needed for getting Content-Disposition information.
Merge pull request #57 from zmughal/plicease/lwp

Merge LWP/HTTP::Tiny header support for #56.