Tweak contribution guidelines, and add info about trailing whitespace.

CONTRIBUTING.md

 * Libraries that are PHP 5.3+, Composer-installable, PSR compliant, tested and documented are preferred.
 * Please make an individual pull request for each suggestion.
 * Use the following format for libraries: \[LIBRARY\]\(LINK\) - DESCRIPTION.
-* Prefix duplicate library names with their vendor or namespace followed by a space: Orno\DI would be Orno DI.
+* 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 categorisaton are welcome.
 * Keep descriptions short and simple. 
 * End all descriptions with a full stop/period.
 * Check your spelling and grammar.
-* New categories, or improvements to the existing categorisaton are welcome.
+* Make sure your text editor is set to remove trailing whitespace.
 
-I try to open a ticket for suggestions each month, so feel free to add anything interesting to it.
+I try to open a ticket for suggestions, so feel free to add anything interesting to that.
 
 Thank you for your suggestions!