bring in Pod::Checker warning about =over without =back
whine when L<> starts or ends with whitespace

For example:

  L< Foo>
  L<Foo >

It leads to confusion.  For example, L<Foo> is a link to the module
Foo, but L< Foo> is a link to the section " Foo" in this document.

This check was in Pod::Checker.  In fact, Pod::Parser was resolving
things the *other* way!  It trimmed whitespace first!
issue a warning on raw | or / in L<text|link> text
tests for recently added warning

also a bit of framework for testing more warnings later
Merge pull request #48 from rjbs/master

New warnings from Pod::Checker.

Plus tests for whine.