Merge 'thunk' tool into 'ouch' tool

Expand with CLI options with usage:

  ouch -e C4Cl6               # enumeration
  ouch -f some_compounds.smi  # list compounds in SMILES file

In general `ouch -?`:

  Common flags:
    -f --file=FILE          List compounds from SMILES file
    -e --enumerate=FORMULA  Enumerate molecular formula
    -? --help               Display help message
    -V --version            Print version information
Merge pull request #3 from mkrauskopf/master

Merge thunk tool into ouch tool
Nice use of CmdArgs