Split MethodInfoAssertions into MethodInfoAssertions  and MethodInfoSelectionAssertions
Split PropertyInfoAssertions and PropertyInfoSelectorAssertions into two classes as done with MethodInfoAssertions.  Also fixed message for BeWritable on the *SelectorAssertions to be consistent with others.  Amazingly these changes did not break any tests.
Split PropertyInfoAssertionSpecs and PropertyInfoSelectorAssertionSpecs.  Added missing tests over `BeWritable` to PropertyInfoSelectorAssertionSpecs.
Added forgotten doc comments
Merge pull request #70 from vossad01/Issues#24#34

Introduce PropertyInfoSelectorAssertions and MethodInfoSelectorAssertions classes