Why is the pronoun I capitalized and the y in the pronoun you is not
capitalized (unless it is after a period)?

According to Dr. Grammar, 

Why is "I" capitalized? 
"Ego has nothing to do with the capitalization of the pronoun I.
Printing and handwriting have everything to do with it. In Middle
English the first person was ich--with a lower-case i. When this was
shortened to i, manuscript writers and printers found it often got
lost or attached to a neighboring word. So the reason for the capital
I is simply to avoid confusion and error. Of course, some writers
refuse to be bound by this convention. Two of our favorites, the poet
e.e. cummings and Don Marquis, author of archy and mehitabel, both
favored the lower-case i" (Morris Dictionary of Word and Phrase
Origins 303).

http://www.drgrammar.org/faqs/#80

Similarly, according to the alt.usage.english FAQ:

Why is "I" capitalized?
   The Barnhart Dictionary of Etymology (Wilson, 1988, ISBN
0-8242-0745-9) says: "~I~ pron. 1137 i; later I (about 1250,
in The Story of Genesis and Exodus); developed from the unstressed
form of Old English (about 725) ic singular pronoun of the first
person (nominative case).  Modern and Middle English I developed
from earlier i in the stressed position.  I came to be written
with a capital letter thereby making it a distinct word and avoiding
misreading handwritten manuscripts.  In the northern and midland
dialects of England the capitalized form I appeared about 1250.
In the south of England, where Old English ic  early shifted in
pronunciation to ich (by palatalization), the form I did not
become established until the 1700's (although it appears
sporadically before that time)." 

http://www.alt-usage-english.org/excerpts/fxwhyisi.html

Search Strategy:

"why is i capitalized"

Have searched about it, and it's only now that i got an answer. I do
like to use the pronoun i because i am a christian.