Improve and clarify guidelines.

CONTRIBUTING.md

 # Contribution Guidelines
 Unfortunately, not every library, tool or framework can be considered for inclusion. The aim of Awesome PHP is to be a concise list of noteworthy and interesting software written in modern PHP. Therefore, suggested software should:
 
-1. Be widely recommended regardless of personal opinion
+1. Be widely recommended
 2. Well known or discussed within the PHP community
 3. Be unique in its approach or function
 4. Fill a niche gap in the market
 
 Also, please ensure your pull request adheres to the following guidelines:
 
-* Software that is PHP 7.0+, Composer-installable, PSR compliant, semantically versioned, unit tested, actively maintained and well documented in English is preferred.
+* Software that is PHP 7.0+, Composer-installable, PSR compliant, semantically versioned, unit tested, actively maintained and well documented in English.
 * Please search previous suggestions before making a new one, as yours may be a duplicate.
 * Enter a meaningful pull request description.
 * Please make an individual commit for each suggestion in a separate pull request.
 * End all descriptions with a full stop/period.
 * Check your spelling and grammar.
 * Make sure your text editor is set to remove trailing whitespace.
+* Your entry has been added alphabetically within the category.
 
 Thank you for your suggestions!