add tests for exceptions
implement exceptions
add stem caching
update docs
Merge branch 'caching' into caching+exceptions

Conflicts:
	lib/Lingua/Stem/Any.pm
cache setter chaining
Merge branch 'exceptions' into caching+exceptions

Conflicts:
	README.pod
	lib/Lingua/Stem/Any.pm
exceptions setter chaining
appease Test::Pod::Coverage