BUG: batch checks if Frame is None
CLN: Get frame_no directly from input incase processing breaks it.
Merge pull request #61 from danielballan/frame-no-tweak

Frame no. tweak
ENH: Add link_df_iter to link an iterable of DataFrames. BTree support is lousy and so currently some tests of link_df_iter() are skipped.
TST: Streamlined test_link.py and added proper tests for link_df_iter()
CLN: link_df_iter() no longer guesses the BTree hash_size from the first frame's data
Merge pull request #57 from nkeim/df_iter

Add linker for an iterable of DataFrames