Add Hash#fetch_nested
Enumerable#sum: Use identity in reduce
Merge pull request #109 from cielavenir/patch-1

bug: Enumerable#sum: Use identity in reduce.
Merge pull request #90 from cielavenir/hash_fetch_nested

Add Hash#fetch_nested.
doc: Improved documentation of Hash#fetch_nested.
bug: Fix Platform#inspect (#110).
Merge branch 'master' of github.com:rubyworks/facets
Add Math::EC for Euler's constant.
Merge branch 'master' of github.com:rubyworks/facets
bug: Fix Enumerable#key_by.
tweak: Add math/ec.rb to math.rb.
:test: Fix instance_extract test.
:bug: Fix Enumerable#sum to take initial value.
:test: Separate test for deep_clone.
:test: Fix test for instance_extract.
:admin: Update HISTORY file.
Further generalize Enumerable#sum.
Add Time::current and improve compatibility with ActiveSupport.
Fix various requires in class files.
:admin: Update MANIFEST.