Upgrade breakpad

[kevinsawicki]

This pull request upgrades breakpad to the version that Electron is using.

Previously I was unable to use walkStack on Linux dumps from Electron 1.4.3. They would fail with the following error:

2016-10-12 16:15:05: simple_symbol_supplier.cc:160: ERROR: Can't construct symbol file path without debug_file (code_file = electron)

• Add linux minidump test
• Test on Linux
• Test on Mac

/cc @zcbenz

[zcbenz]

👍 Looks good to me.