Add implementation of the Fortuna CSPRNG

Unit tests verified against pycrypto. Closes #103.
Fix lifetime bound errors.
Merge pull request #108 from Ryman/master

Fix lifetime bound errors.
Merge pull request #104 from apoelstra/fortuna

Add implementation of the Fortuna CSPRNG
Fix deprecation warnings
Merge pull request #109 from ebfe/deprecated

Fix deprecation warnings
Update Cargo script (change [[lib]] to [lib])
Fix build error
Remove build warnings
I changed this file's source code more rust-like (especially for functions' returned values)
Merge pull request #110 from GuillaumeGomez/master

Few fixes and updates
Update .travis.yml file now that Travis-CI supports Rust natively
Merge pull request #111 from DaGenix/fixups

Update .travis.yml file now that Travis-CI supports Rust natively
Update for Rust syntax changes

extern crate foo = "bar";
is now
extern crate "bar" as foo;
as per RFC 47.  Details at https://github.com/rust-lang/rust/issues/16461
Merge pull request #112 from jamesluke/master

Update for Rust syntax changes