RF: add dipy_ prefix to scripts lacking same

Standardize on dipy prefix for scripts
RF: remove .py extensions from scripts

To follow debian policy 10.4 on script file names:

http://www.debian.org/doc/debian-policy/ch-files.html
RF: remove duplicate sh_estimate.py script

It is an older version of the dipy_sh_estimate script
RF: specify script names

This allows us to have files in the ``bin`` directory that we don't
install as scripts.
NF: add windows script installer wrapper

Copied from nibabel
RF: fit_tensor no-arg return code to match others

The other scripts use argparse, which returns error code 2 for no
arguments.  dipy_fit_tensor uses optparse, so has to specify the error
return code.  Make it match the argparse scripts.
TST: add smoke tests for scripts

Need tests for script behavior too.
RF: add copy of argparse for python 2.6 support

We're using argparse, but Python 2.6 does not have it by default.  For
now install a copy for us to use instead.
RF: use argparse copy to avoid argparse dependency
Merge pull request #159 from matthew-brett/rename-install-test-scripts

Rename install test scripts