Removed getline, various small tweaks

* array_util
** concat_array now dynamically resizes to an appropriate size
* declension
** Updated calls to concat_array
** Made prompt for adjectives more intuitive
* input
** Removed use of getline, now directly processing stdin
* parts_of_speech
** Updated ADJ_ENDINGS to fit with adjective prompts
* verbs
** Updated calls to concat_array