it\'s quite common and it\'s just an abbreviation of \"and\" or \"in\" or words ending in \"ing\"( I don\'t think you want to use those in your English homework, unless you quote someone\'s speech).
examples of \'n abbreviations off the top of my head:
tounge in cheek ...tounge\'n cheek
smoking gun....smok\'n gun
I don\'t go out anymore with the new baby\'n all (...with the new baby and all)
:)