web app to create heat profiles

sim.py supports following heat profiles, which provides greater accuracy.

Here's an example: Sn63Pb37 solder paste.

it would be cool to have a web app that lets you interactively move around critical points and output a text file.
- Right now we only support straight lines

So for the solder paste it would look like:
```
0 22
90 150 # soaking zone start
190 180 # soaking zone end
220 220 # reflow zone start
270 180 # reflow zone end
```

Extra points for clean alignment, e.g.:
```
0 22
90 150 # soaking zone start
190 180 # soaking zone end
200 220 # reflow zone start
270 180 # reflow zone end
```