Allow end as a substring of vertex id

Jison adds \b (word boundary) to literal string patterns by default.
It does so, because it doesn't follow traditional match-longest
approach, but does match-first instead. Without including word
boundaries, it'd be hard to distinguish between a keyword and
identifier.

The pattern for `end` keyword is not a simple string literal - it
swallows trailing whitespace, so we have to add \b manually.

This partially fixes #184 - at least now `end` behaves the same as other
keywords: it can be used as a prefix and infix, but not as a suffix.

To solve this issue completely, ALPHA pattern would have to match
multiple letters, which is a much bigger change.

src/diagrams/flowchart/parser/flow.spec.js

@@ -308,6 +308,18 @@ describe('when parsing ',function(){
         expect(edges[0].text).toBe('');
     });
 
+    it('should handle node names with "end" substring',function(){
+        var res = flow.parser.parse('graph TD\nendpoint --> sender');
+
+        var vert = flow.parser.yy.getVertices();
+        var edges = flow.parser.yy.getEdges();
+
+        expect(vert['endpoint'].id).toBe('endpoint');
+        expect(vert['sender'].id).toBe('sender');
+        expect(edges[0].start).toBe('endpoint');
+        expect(edges[0].end).toBe('sender');
+    });
+
     it('should handle open ended edges',function(){
         var res = flow.parser.parse('graph TD;A---B;');