[iotile-build] breathe/sphinx dependency fix

[x24ling]

On april 7th, breathe recently upgraded to 4.15.0, which now depends on sphinx 3.0.0.
https://github.com/michaeljones/breathe/commits/master

According to our setup requirements, our dependencies break this:

coretools/iotilebuild/setup.py

Lines 29 to 41 in 123f46a

	install_requires=[
	"crcmod>=1.7.0",
	"iotile-core>=5.0.13,<6",
	"sphinx>=2,<3",
	"jinja2>=2.10.0,<3",
	"breathe>=4.11.0,<5",
	"pygtrie>=2.0.0,<3",
	"toposort>=1.5.0,<2",
	"wheel>=0.33",
	"setuptools>=40.8",
	"pycparser>=2.17,<3",
	"pyparsing~=2.2.0"
	],

We need to either

1. Force breathe to stick to 4.14.1
2. Bump sphinx to >=3,<4",

[timburke]

@x24ling I would just pin breathe for now and then we can update later.

[x24ling]

cool, i'll take care of this