rootpy script: use find_files in sum() to avoid limit on number of cmd args
yield full path in find_files
minor edit
rootpy script: catch ROOTErrors if ROOT can't open the TFile
clean exit on KeyboardInterrupt
Merge pull request #168 from ndawe/master

More robust error handling in the rootpy script (and other minor fixes)
update README
remove a few bullets
first pass response to @pwaller's comments
second pass response to @pwaller's comments
make std::vector code
minor edit
shorten bullet
respond to @pwaller's comments
Merge pull request #169 from ndawe/master

Update README
add ghp-import script and entry in Makefile to update gh-pages
preserve_current_directory in TreeChain
note about docs
show which tests are run and don't test extern
add TreeChain unit tests