* fit_betasbp_cut.py
  - fixed 'dof' calculation with 'n-p-1'
  - fixed 'par_eps' calculation/configuration
  - added 'fit_model_bounds' using 'scipy.optimize.minimize' to
    perform function minimization with bounds
  - split the data cut section to function 'cut_data'
  - added argument 'options' to 'fit_model_bounds'
* marx_pntsrc.py
  Run MARX simulation on a given list of point sources, merge the
  output simulation results, and finally convert into FITS image.
* blanksky_add_time.py
  Add a time column for the chandra blanksky event file.
  The time data are generated with a uniform distribution
  between TSTART and TSTOP.

* added 'fit_model_bounds' using 'scipy.optimize.minimize' to
  perform function minimization with bounds
* split the data cut section to function 'cut_data'
* added argument 'options' to 'fit_model_bounds'

fit_betasbp_cut.py:
* replace getopt with 'argparse'
* added 'get_parameter' to process model parameter initial value and bounds
* support read parameter bounds from input file
* added options '--s0', '--rc', '--beta', '--const' to get paramter
  initial values and bounds
* renamed 'fit_beta_model' to 'fit_model', and added argument 'func' to
  support other models

fit_betasbp_cut.py:
* added support ignore the data points whose radius value less than the given value.

fit_beta_model.py
* fit provided data with beta model
* ignore the inner-most n data points for the fitting