[RFC] Supports multiples PID (-p PID1 -p PID2 ...)

[moylop260]

Make sure that these boxes are checked before submitting your issue:

• Include the output of pyflame -v
• pyflame 1.6.6 linux-gnu x86_64 (ABI list: 26 34 36)
• Include the exact version of the Python interpreter you are profiling.
• Python 3.5.3
• Include the exact text of any error messages.
• I don't have any error message really.

I'm using the following python app:

• https://github.com/odoo/odoo

It has a parameter called workers
Using this feature many python process PID are started.

pyflame currently doesn't support -p PID1 -p PID2 -p PID3 since that I just tested and it is not collecting the full information of a particular process.

I need using a

pyflame ... -o test_1.flame -p PID1
pyflame ... -o test_2.flame -p PID2
pyflame ... -o test_3.flame -p PID3
pyflame ... -o test_4.flame -p PID4

After I just transform all output to svg using:
flamegraph.pl test_*.flame >test.svg

Now It collects the full information of the particular process.

IMHO It could be a good feature if pyflame supports multiple PID with -p