Prevent from including header content multiple times
Say libcangjie2 is a C library and use C89 syntax in example
Fix broken documentation URL
Merge pull request #17 from linquize/README-c89

Improve README.md

  1. Make the example C89 compatible.
  2. Fix broken documentation URL
  3. Minor documentation improvements.
Merge pull request #14 from linquize/include-twice

Merge branch 'include-twice' of https://github.com/linquize/libcangjie2
Prevent from including header content multiple times

Conflicts:
	src/cangjieerrors.h