Fix of #8

Finally added Batch API support.

Now, it is possible to specify PAM service name to be used for authentication of LFS server users.

For example:

./lfs_server.sh -pam login

will use built-in login PAM service. It is usually defined in /etc/pam.d/login file.

This is mostly infrastructure release. The only functional change is shutdown of async engine on SIGINT and SIGTERM signals.

Infrastructure changes:

• Setup of Travis continuous integration
• Most of use cases are now covered (tests run automatically by COVERALLS)
• Switched to OCaml 4.02.3 compiler and new async library
• Added libffi library to Mac OS X binary distribution

Changes:

• Validation of uploading objects (SHA-256 digest is calculated and compared with provided OID)
• Incomplete/broken temporary files are removed automatically
• Uppercase OIDs are rejected

Changes:

• Added logging (use -verbose flag to log all connections)
• Better handling of interrupted connections
• Better error messages
• Fixed URLs for HTTPS protocol
• Scripts for packaging
• Added Lfs_config

Implemented:

• Git LFS API except for Authentication
• HTTP and HTTPS protocols support
• Local object storage (ROOT/.lfs folder)