Replace 'use base' with 'use parent' in lib/

'base.pm' is an old module for which usage is deprecated.
'parent.pm' is its recommended replacement and is in the perl core
since 5.10.1.

This patch replaces all instances of 'use base' with 'use
parent'. In documentation both modules are mentioned.
Replace 'use base' by 'use parent' in t/ (step 1)

Replace 'use base' by 'use parent' for the simple cases (the class is in
a separate file that 'parent' will load).
Replace 'use base' by 'use parent -norequire' in t/ (step 2)

Replace 'use base' by 'use parent -norequire' for inline classes in t/.
Add parent.pm as a runtime dependency

parent.pm is in core since 5.10.1.
Replace 'use base' by 'use parent' in examples/ and inc/
Merge pull request #35 from dolmen/topic/base-to-parent

Move from base.pm to parent.pm