Raise minimum PHP version to 7.0+ in guidelines

CONTRIBUTING.md

@@ -1,16 +1,16 @@
 # 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: 
+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
 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  
+4. Fill a niche gap in the market
 
 Self-promotion is frowned upon, so please consider seriously whether your project meets the criteria before opening a pull request, 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, semantically versioned, united tested and well documented in English is preferred.
+* Software that is PHP 7.0+, Composer-installable, PSR compliant, semantically versioned, united tested and well documented in English is preferred.
 * 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.
@@ -18,7 +18,7 @@ Also, please ensure your pull request adheres to the following guidelines:
 * 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.
-* Please keep descriptions short, simple and unbiased. No buzzwords or marketing jargon. 
+* Please keep descriptions short, simple and unbiased. No buzzwords or marketing jargon.
 * End all descriptions with a full stop/period.
 * Check your spelling and grammar.
 * Make sure your text editor is set to remove trailing whitespace.