Given two words as Strings, determine if they are isomorphic. Two words are called isomorphic if the letters in one word can be remapped to get the second word. Remapping a letter means replacing all occurrences of it with another letter while the ordering of the letters remains unchanged. No two letters may map to the same letter, but a letter may map to itself.
*
* Example:
* given "foo", "app"; returns true
* we can map 'f' -> 'a' and 'o' -> 'p'
*
* given "foo", "boa"; returns false
* we can map 'f' -> 'b', 'o' -> 'o', we can't map 'o' -> 'a'
*
* given "bar", "foo"; returns false
* we can't map both 'a' and 'r' to 'o'
*
* given "turtle", "tletur"; returns true
* we can map 't' -> 't', 'u' -> 'l', 'r' -> 'e', 'l' -> 'u', 'e' ->'r'
*
* given "ab", "ca"; returns true
* we can map 'a' -> 'c', 'b' -> 'a'
*/
