Correct tz_database documentation, code expects 'last' not -1.
Added Makefile rule to build tz_index.hrl.
Prefer underscores in timezone names, but accept spaces.
Update timezone database from Olson 2013i.

Some adjustments had to be made for the erlang_localtime format; these
are noted in the database file.
Add more localtime_dst tests.

Some of these tests are currently failing.
Merge pull request #10 from dhull/update-database

Update time zone database from Olson database