[WIP] Added the possibility to have a smiley glue to open and close tag

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes
| Tests pass?   | yes
| Related tickets | #75
| License       | MIT

* TODO:
  - [ ] Added tests with a large set of posts with complex BB code https://github.com/milesj/decoda/issues/75#issuecomment-49655654
  - [ ] Write good commit messages, for this changes it's important.