Merge pull request #95 from vhbit/custom-build

New build system
Add XTS-AES mode
Merge pull request #96 from coyotebush/xts

Add XTS-AES mode
Move AES XTS support to a feature
Fix travis features
Impl Error for SslError
Fixed compilation errors related to namedspaced enums
Merge pull request #98 from jamesrhurst/namespaced-enums

Fixed compilation errors related to namedspaced enums
Remove Zero and One impls
New build system
New build system
Cert loading from PEM & restructuring 

- Added cert loading

- Extracted X509 tests

- Extracted `hash_str_to_vec` function into `utils.rs` as it is used 
  in a couple of tests now

- Fixed `hash_str_to_vec`, funny enough prev test with it was working 
  because I’ve made another mistake by providing VerifyNone instead of 
  VerifyPeer and those 2 mistakes compensated each other. Since
  `hash_str_to_vec` is private there was no errors on client code
Better thread working

Works pretty stable for me, although I'm not sure it is 100% thread safe yet.

Changes mostly inspired by https://www.arangodb.org/2014/07/08/started-hate-openssl :

- Switched to newer CRYPTO_THREADID API for Unixes

- Clearing errors queue before every critical operation
Simplified SslStream.write, updated comments
Locking internal buffer from same thread access

If cloned stream was used in the same thread
WIP: erase later
Update to nightly
Fixed invalid rebase