Adopted astropy file formats for spectrum and py_wind, and updated py_read_output.py

Spectrum formats are now

```
Freq.        Lambda  Created  Emitted   CenSrc  Disk     Wind     HitSurf Scattered A10P0.50 
1.499187e+15 1999.700  2.07e-12 2.07e-12 2.07e-12        0        0        0        0 5.39e-12
```

i.e. the headers are not commented.

py_wind outputs are now

```
# TITLE= "sv.ne.dat"
# Coord_Sys CYLIND
x z var inwind i j
1.4000e+09 3.5000e+08 0.00e+00  -2   0   0
1.4000e+09 8.0805e+08 0.00e+00  -1   0   1
```

for 2d systems and 

```
# TITLE= "sv.ne.dat"
# Coord_Sys SPHERICAL
r var inwind i 
1.4000e+09  0.00e+00  -2   0  
```

for 1d systems.

This is originally raised in issue #122 . Diagnostic outputs should be updated once #120 is merged. 

This pull request has also updated some python scripts in py_progs. Using these is described [here](https://github.com/agnwinds/python/wiki/Useful-python-commands-for-reading-and-processing-outputs).