add fake ciphers for salsa20 chacha20
implement encrypt() function
refine the sodium support
update configure file
update Makefile
fix some bugs
integrate libsodium as a submodule
integrate libsodium as a subproject
update gitignore
update autoconf tools
update configure.ac
bump version
Merge pull request #183 from madeye/sodium

Add support of salsa20 and chacha20