Change references of 'EMail' to '[Ee]mail'

Depending on if it was the beginning of the sentence the EMail would
become 'Email' or 'email'.

Some references of 'Email' were changed to 'email' as well as those were
not in the beginning of a sentence.

A few places some consistency of capitalised email address (made lower
case) were changed to match other places of the same pattern.

1990/rules

@@ -38,7 +38,7 @@ RULES:
 ---header items---
 name:    	Your name, of course!
 org:		School/Company/Organization
-email address:	Email address from a well known site, or in a registered domain
+email address: email address from a well known site, or in a registered domain
 postal address:	Postal address
 		include your country as well
 environment:	Indicate the Hardware 
@@ -102,12 +102,12 @@ X If your entry does not end in a newline, leave a final 'E' on the end. E
 	   
 	    ...!{sun,pacbell,uunet,utzoo,pyramid,amdahl}!hoptoad!obfuscate
 
-       We will attempt to Email a confirmation of receipt of contest
-       entries, however since Email is not reliable you may not receive it.
+       We will attempt to email a confirmation of receipt of contest
+       entries, however since email is not reliable you may not receive it.
        We regret that we can no longer accept entries via postal mail.
 
     7) Each person may submit up to 8 entries.  Multiple entries must
-       be sent in separate Email letters.
+       be sent in separate emails.
 	
     8) Entries that can not be built automatically in a portable makefile 
        are not allowed.  (e.g., don't use #include "/dev/tty")