Release 0.7.1

Features/news:

• Added detected language to return value of search_dates()
• Performance improvements
• Refreshed versions of dependencies

Improvements:

• Fixed unpickleable DateTime objects with timezones
• Fixed regex pattern to avoid new behaviour of re.split() in Python 3.7
• Fixed an exception thrown when parsing colons
• Fixed tests failing on days with number greater than 30
• Fixed ZeroDivisionError exceptions