test => no zeros & one zero
test => large N! trailing zeros
refactoring => seperate code from test
Merge branch 'number_of_trailing_zeros_of_N!'
add test into all-tests.html
test => empty dictionary
test => empty word
test => one word
test => continuous words
test => invalid word
test => repeat word
test => greedy matching
refactoring => using ! instead if
Merge branch 'valid_string'