Separated the PalindromeTester class into PalindromeCheck class, which
checks the words, and PalindromeCheck_Test class, which simply performs
the same test run the original class used to. This means the
PalindromeCheck class can now be copied and reused in other projects as
it is.

Changed the checkWord to a static method, instantiation of the
PalindromeCheck class no longer required, simply make a static call to
PalindromeCheck.checkWord.