[fix] Added some OS X files (.DS_Store) to .gitignore
[add]Combination of wrong sentences with valid sentences.

There're some errors when you try to extract sentences from text just by using punctuation marks. For instance when you use abbreviations.
**Example:** 'I don't eat fat food. E.g. I don't eat pies.'

The result of splitting this text on sentences by punctuation marks will be:
* 'I don't eat fat food.'
* 'E.'
* 'g. '
* 'I don't eat pies'

When you will try to add a sentence 'g. ' to your sentences, the method won't add new element to array. Instead, the method just concatenate new sentence with last sentence in the array.
So if you will sequentually add these sentences to array, the result array will be:
**['I don't eat fat food.', 'E.g. ', 'I don't eat pies']**