Rename assertion -> anchor. Fixes #47.
Do only construct an "alternative" AST entry if it has more than two child elements. Fixes #41.
Fix review comments from @mathiasbynens
Merge pull request #49 from jviereck/cleanup

AST Cleanup. Fixes #47 and #41.
Remove the lastMatchIdx etc. Fixes 48
Merge pull request #53 from jviereck/fix_48

Remove the lastMatchIdx etc. Fixes 48
Cleanup escaped and characterClassEscape types