Fix typos in Ch03 plus Whatcha doin'

sytem -> system
he past -> the past
cas access -> has access to
futher -> further
choosen -> chosen
specifing -> specifying
refelct -> reflect
Advacned -> Advanced
convienence -> convenience
fundemental -> fundamental
Carteisan -> Cartesian
therally -> literally 
syncronously -> synchronously
asyncronously -> asynchronously
syncronous -> synchronous
Whatcha you doing -> Whatcha doin' (you is a hendiadys, possibly a tautology, as the suffix -cha is a crasis for "are you"), the proposed form is the most common spelling
interal -> internal
indepndently -> independently 
while that make, .. that -> while this makes .., it
etc -> etc.
legnth -> length
stroage -> storage
breifly -> briefly