Added plot.py, a script for plotting energies
Pull branch "plotit" from GitHub

Apparently, I can't push plotit until I pull. I need to push this
because the "plotit" branch on GitHub doesn't even have plot.py.
Merge branch 'master' into plotit
Better filetype handling. More error checking

plot.py now has an additional bit of error checking. plot.py
currently relies on the option --scanind being used with
calculate.py. If the error associated with that missing occurs,
it lets you know.

Can now save to multiple filetypes at once.
Fixed error with importing MM3* angles

The value for param_type was wrong for MM3* angles (equilibrium
values and force constants) and the value for mm3_col was wrong
for the angle force constants.