Update data tables to Unicode 7.0.0

Updates:
1. Updates the `data_generator.rb` script. This script now runs on a modern version of `ruby` (>1.8) and has the hard-coded data tables replaced with file reads from the appropriate Unicode data (UNIDATA) files.
2. Provides a new `Makefile` target, `update`, which automatically downloads the relevant UNIDATA and runs `data_generator.rb` to produce the file `utf8proc_data.c.new`.
3. Updates `utf8proc_data.c` to the output generated by running `make update` against UNIDATA v7.0.0

Observations:
1. There are [`#define`d constants in `utf8proc.c`](https://github.com/JuliaLang/libutf8proc/blob/e41bd981cbc2242b5e44da0bef48fd0f57065fed/utf8proc.c#L64) which may in principle have changed from v5.0 to v7.0, such as the constants marking the location of Hangul, Unihan, etc. I haven't checked them and it's probably not worth recomputing for each new Unicode version.
2. It looks like `utf8proc` implements an [internal processing mode called `LUMP`](https://github.com/JuliaLang/libutf8proc/blob/e41bd981cbc2242b5e44da0bef48fd0f57065fed/utf8proc.c#L239), which is briefly described in `lump.txt`. As far as I can tell, this is a custom normalization mode which is separate from the Unicode standard, but I think we'll want to use these.

Closes #1