fix some typos

[rookiemonkey]

beers_spec

• typo (line 18) - should be a period instead of a comma

clearance_spec

• typo (line 16) - should be clearance instead of cleraance

cupcakes_spec

• typo (line 7) - should be Cupcakes instead of Cupcake
• wrong expectation (line 24) should be Caramel instead of Carrot because caramel cupcake has the largest amount of sugar

dog_spec

• typo (line 15) should be hungry? instead of hungry

student_spec

• typo (line 36) should be E instead of F because slack_off decreases the grade only by one step
• typo (line 59) should be .study instead of .slack_off since the 'it' block is already testing the .study method
• typo (line 61) should be E instead of B since the grade will be stuck on F because of invoking slack_off multiple times and studying will only increase the grade by one level

yak_spec

• type (line 8) should be .hairy? instead of .hairy. line 16 has .hairy? method but line 8 has no question mark. preferred w/ ? instead since method returns a boolean

removed xit for the following spec files

• dog_spec
• door_spec
• drops_spec
• floor_spec
• kid_spec
• leather_chair_spec
• milk_bottle_spec
• money_spec
• music_spec
• person_spec
• pills_spec
• roll_call_spec
• santa_spec
• student_spec
• teeth_spec
• tire_spec
• wallet_spec
• water_spec
• yak_spec