Fix tightlist error on pdf generation
Fix tightlist error on pdf generation

When generating the pdf I got
```
! Undefined control sequence.
l.440 \tightlist
```

This was a bug (already fixed) also on pandoc templates.
sdiehl/write-you-a-haskell,FranklinChen/write-you-a-haskell,sdiehl/write-you-a-haskell,sdiehl/write-you-a-haskell,yupferris/write-you-a-haskell,FranklinChen/write-you-a-haskell,FranklinChen/write-you-a-haskell,sdiehl/write-you-a-haskell,FranklinChen/write-you-a-haskell,yupferris/write-you-a-haskell,FranklinChen/write-you-a-haskell,sdiehl/write-you-a-haskell,yupferris/write-you-a-haskell,yupferris/write-you-a-haskell,sdiehl/write-you-a-haskell,yupferris/write-you-a-haskell,FranklinChen/write-you-a-haskell,yupferris/write-you-a-haskell