Better pdf table names

Fixes an indexing / display bug where tables extracted from PDFs would have a `name` attribute of something weird like `Table 0 of 1 on page 0 of 3`.

No tests because I couldn't work out how to get my environment set up, and my lunchtime timebox was up (I created a `virtualenv`, activated, and then pip installed `requirements-test.txt`, but `nosetest` still skipped the two pdf tests at the end of `test/test_read.py`)

If somebody could run the tests and confirm this works, then merge it, that'd be really handy. This bug is currently blocking this ticket in the Table Xtract tool: https://github.com/scraperwiki/magic-table-scraper-tool/issues/219