Improve flip script with new features

Demo:
hubot flip
hubot> (╯°□°）╯︵ ┻━┻
hubot unflip
hubot> ┬──┬ ノ( º _ ºノ)
hubot rage flip
hubot> (ノಠ益ಠ)ノ彡 ┻━┻
hubot flip java
hubot> (╯°□°）╯︵ ɐʌɐɾ
hubot rage flip .NET
hubot> (ノಠ益ಠ)ノ彡 ⊥Ǝᴎ˙
hubot unflip ɐʌɐɾ
hubot> java ノ( º _ ºノ)
hubot flip me
hubot> (╯°□°）╯︵ ʃʃǝɥS
hubot unflip me
hubot> Shell ノ( º _ ºノ)
Merge pull request #1097 from spajus/improved_flip

Improve flip script with new features