Ensure Spacing only flags terminal punctuation

Fixes #14.

Author: jdkato

Microsoft/Spacing.yml

@@ -4,5 +4,5 @@ link: https://docs.microsoft.com/en-us/style-guide/punctuation/periods
 level: error
 nonword: true
 tokens:
-  - '[.?!] {2,}[A-Z]'
-  - '[.?!][A-Z]'
+  - '[a-z][.?!] {2,}[A-Z]'
+  - '[a-z][.?!][A-Z]'

features/rules.feature

@@ -153,5 +153,5 @@ Feature: Rules
     When I test "Sentences"
     Then the output should contain exactly:
       """
-      test.md:5:22:Microsoft.Spacing:'. T' should have one space.
+      test.md:5:21:Microsoft.Spacing:'y. T' should have one space.
       """

fixtures/Sentences/test.md

@@ -3,3 +3,5 @@
 this is a sentence. so is this one.
 
 This sentence is okay.  This one is not.
+
+The latest version of .NET Core is awesome!