Update AT24.md

Fix a typo, and document changes to AT24,js (specifically the removal of the i2caddress argument from most functions, which wastes more memory than you get back from not needing multiple eeprom objects - not to mention the trouble it will cause when using memory of different pagesize.
Update AT24.js

Remove i2ca argument from every function. It's better to make multiple eeprom objects, and that way you can have devices with different page sizes in use, and the module is smaller for the majority of use cases where a single EEPROM is in use.

Also, renamed arrayToString to aToS to reduce memory footprint by a few jsvars.
Update AT24.md

Fix another typo, and change arrayToString() to aToS()
Create AT25.md
Create AT25.js

Support for AT25 EEPROM chips
Update AT24.md

Fix minor error
Merge pull request #96 from SpenceKonde/master

Add support for AT25 series, reduce memory footprint of AT24 series.