Create a function that replaces all the vowels in a string with a specified character.
replaceVowels("the aardvark", "#") ➞ "th# ##rdv#rk"
replaceVowels("minnie mouse", "?") ➞ "m?nn?? m??s?"
replaceVowels("shakespeare", "*") ➞ "sh*k*sp**r*"
All characters will be in lower case.