[LANG] Checked Functions PR

[Aleksander Ściborek]

I've just created  pull request
<https://github.com/apache/commons-lang/pull/401> to a set of functions
which are wrappers for standard interfaces from java.util.function.
The idea behind this is that you can create an instance of a function which
throws a checked exception and then using a static method create an
instance of standard function which invocation of a checked functions.
Those interfaces were designed in order to using stream API easier