Add requirements for code files to CONTRIBUTING
Add requirements for code files to CONTRIBUTING

Ayrx/cryptography,bwhmather/cryptography,Ayrx/cryptography,bwhmather/cryptography,Lukasa/cryptography,sholsapp/cryptography,Lukasa/cryptography,dstufft/cryptography,Hasimir/cryptography,bwhmather/cryptography,skeuomorf/cryptography,skeuomorf/cryptography,skeuomorf/cryptography,Hasimir/cryptography,Hasimir/cryptography,Hasimir/cryptography,kimvais/cryptography,sholsapp/cryptography,skeuomorf/cryptography,dstufft/cryptography,dstufft/cryptography,kimvais/cryptography,sholsapp/cryptography,kimvais/cryptography,Ayrx/cryptography,sholsapp/cryptography,dstufft/cryptography,Lukasa/cryptography,dstufft/cryptography,bwhmather/cryptography,Ayrx/cryptography,glyph/cryptography,glyph/cryptography,kimvais/cryptography