Improve contribution guidelines

CONTRIBUTING.md

@@ -1,15 +1,24 @@
 # Contribution Guidelines
-Please ensure your pull request adheres to the following guidelines:
+Unfortunately, not every library, tool or framework can be considered. The aim of Awesome PHP is to be a concise list of noteworthy and interesting software written in modern PHP. Therefore, suggested software should: 
 
+a) Be widely recommend regardless of personal opinion
+b) Well known or discussed in the PHP community
+c) Be unique in its approach or function
+d) Fill a niche gap in the market
+
+Self-promotion is frowned upon, so please seriously consider whether your project meets the above criteria before making a suggestion, otherwise it may be closed without being reviewed.
+
+Also, please ensure your pull request adheres to the following guidelines:
+
+* Software that is PHP 5.5+, Composer-installable, PSR compliant, united tested and well documented are preferred.
 * Please search previous suggestions before making a new one, as yours may be a duplicate.
-* Libraries that are PHP 5.3+, Composer-installable, PSR compliant, tested and documented are preferred.
 * Enter a meaningful pull request description.
 * Please make an individual commit for each suggestion in a pull request.
-* Put a link to each library in your pull request ticket so they're easier to look at.
+* Put a link to each library in your pull request ticket so it's easier to review.
 * Use the following format for libraries: \[LIBRARY\]\(LINK\) - DESCRIPTION.
 * Prefix duplicate library names with their vendor or namespace followed by a space: Foo\Bar would be Foo Bar.
 * New categories, or improvements to the existing categorisation, are always welcome.
-* Keep descriptions short and simple. 
+* Keep descriptions short, simple and unbiased. 
 * End all descriptions with a full stop/period.
 * Check your spelling and grammar.
 * Make sure your text editor is set to remove trailing whitespace.