Add clean files from a list

Add function that apply can use to clean files.
Remove space before stop words

Add a remove of leading spaces prior to calling remove_stopwords().
There are instances where removal of punctuation left a leading space,
which caused remove_stopwords() to not match.
Move split before remove_stopwords

Moved split from beginning of cleanText() to just before
remove_stopwords() since prior functions do not need. This also handles
cases were removing punctuation causes leading and trailing spaces on
stop words.