ENH: New tracking function accepts an iterator to conserve memory.
API/CLN: Distinguish link_trackpy, link_iterator, and link.
ENH: Make link use custom trackpy that accepts a generator.
ENH: Link features in an HDFStore on unlimited size using LinkOnDis.
CLN: Expose more parameters to link, and add better Exceptions to LinkOnDisk.
TST: Unit tests on uncontrolled data are problematic.
TST: Basic smoke tests for LinkOnDisk.
TST: Have Travis install PyTables from binary, not source.
Merge branch 'track-on-disk'