GPL-be-gone

This release contains changes relevant only to Darwin. If you are not running MacOS, you do not need to upgrade.

v4.0.0 saw a move from AGPL to MIT-3; this was started a year ago by the original gotop author, and we finally pulled the trigger and made the switch. MIT-3 is not compatible with the GPL in that GPL code may not be used in an MIT-3 licensed project, and changes had been made to remove GPL dependencies. However, one of the dependencies incorrectly licensed itself as MIT, as it, itself, dependended on GPL code -- and thereby "infected"[1] all of the downstream projects using that code. For gotop, it meant that the code supplying thermal sensor data on OSX could not be used.

This release removes the dependency that referenced GPL code, and so makes gotop (and, in particular, Darwin builds) compliant again.

The Go linker excludes code it doesn't use; this particular section of code is also fenced by a GOOS flag, and the compiler didn't use or load the code that depended on the GPL-infected dependency except when being built for Darwin. This means that no GPL code was referenced or used to build binaries for OSes other than Darwin. IANAL, but I believe this means that only Darwin users need upgrade to this version; binaries for other system should essentially be unchanged.

[1] "Infect" has negative connotations, but its use here references the truth that only GPL code can use GPL code, and so by using GPL dependencies projects are legally forced to also use the GPL license. Many people do believe this is a negative thing, but I don't except in that it does introduce an impediment to writing software.