Add digits trick

* Ruby 2.4

Changes:

* Add tricks/digits.md file
* Add tricks/source_code/digits.rb file

Author: IlyaUmanets

tricks.md

@@ -22,6 +22,7 @@ The majority of these Ruby Tricks were extracted from James Edward Gray II [talk
 * [Head tail](tricks/head-tail.md)
 * [Inject](tricks/inject.md)
 * [Inspecting the source with script lines](tricks/inspecting-the-source-with-script-lines.md)
+* [Integer#digits](tricks/digits.md)
 * [Iterating over specific types](tricks/iterating-over-specific-types.md)
 * [Lambda your own syntax](tricks/lambda-your-own-syntax.md)
 * [Memoization](tricks/memoization.md)

tricks/digits.md

@@ -0,0 +1,17 @@
+### Integer#digits
+
+```ruby
+awesome_number = 12345
+
+p awesome_number.to_s.chars.map(&:to_i).reverse
+
+# Result:
+# [5, 4, 3, 2, 1]
+
+p awesome_number.digits
+
+# Result:
+# [5, 4, 3, 2, 1]
+```
+
+[View Source](source_code/digits.rb)

tricks/source_code/digits.rb

@@ -0,0 +1,11 @@
+awesome_number = 12345
+
+p awesome_number.to_s.chars.map(&:to_i).reverse
+
+# Result:
+# [5, 4, 3, 2, 1]
+
+p awesome_number.digits
+
+# Result:
+# [5, 4, 3, 2, 1]