Merge pull request #78 from snatchev/patch-1

Update README regarding Keychain Access and p12 w/o passwords

README.md

@@ -112,6 +112,15 @@ To get a list of available options run:
     pem --help
 
 
+### Note about empty `p12` passwords and Keychain Access.app
+
+`pem` will produce a valid `p12` without specifying a password, or using the empty-string as the password. 
+While the file is valid, Mac OSX's Keychain Access will not allow you to open the file without specifing a passphrase.
+
+Instead, you may verify the file is valid using OpenSSL:
+
+    openssl pkcs12 -info -in my.p12
+
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 ## Environment Variables