PLT-482 Add Guavate.not(Predicate)

Negating a predicate can be harder than necessary
PLT-482 Add checked exception handling

Allow checked exceptions to be handled in lambdas
PLT-482 Add checked exception handling

Clearer Javadoc
PLT-482 Add checked exception handling

Javadoc and Tests
Merge pull request #28 from OpenGamma/topic/PLT-482

Add checked exception handling