removed files...
forgot to add a file
added print_tagset and trim_below_abundance code, and associated scripts
documented count-shared-kmers a bit
ignore Pyrex output file
vector/uniqify scripts
commented extract_unique_paths; N->G in assembly-diff-2.py
updated
hamming-distance-1 scripts
replace N with G
fix bug where short sequences are ignored
rearranged .gitignore w/temp files on bottom
cleaned up test data file mess.

specifically,
 - most data files for tests are now under tests/test-data/
 - all test data requests go through a function in khmer_tst_utils
 - all output files are placed in temp directories & cleaned up
inaugurated sandbox
some initial script docs & tests
add tests for filter-stoptags and filter-abund.  also updated binary formats.
removed apparently unnecessary files
removed apparently unnecessary files
added helpful output
added normalize-by-min/med scripts for digital normalization