Improved string writing speed

Broke out the converting of characters to codes and then converting the
codes into bytes into two methods.  Also preallocated the codes buffer and the
bytes buffer
Increased string reading speed

Split out the converting from bytes to character codes and then
character codes to characters from one method to two.  Also pre allocated
the byte buffer and code buffer.
Wrote documentation for string writer and reader
Version bump to 0.1.1