allow callback to determine if a get() returns no value

When result was false (the old behavior), callback could not tell if the value was false or if the key was not found. This allows the callback to differentiate between the two
Correct typo 'you Memcached' > 'your Memcached'
Rephrase paragraph for readability
Correct typo 'for' > ''
Restructure paragraph for readability
Correct typo 'There 2' > 'There are two'
Merge pull request #189 from fcolas6013/master

Documentation edit: correct typos, and rephrase two paragraphs
Phrase correction
Rephrase Options paragraph
Rephrase description of Options
Correct typo/missing verb in description options
Focus on vertical reading given 'DRY' for func/arg
Merge pull request #190 from fcolas6013/master

Rework README for readability, 'DRY', consistency, and sentences
simple typo
Merge pull request #191 from bahamas10/patch-1

simple typo
Update README.md

it should be a spell mistake
Merge pull request #193 from yyydao/patch-1

Update README.md
changing port 11212 to 11211
Merge pull request #108 from kahing/patch-1

allow callback to determine if a get() returns no value
Add server address to connection error message