Add CHANGES.md

[fingolfin]

For users it is extremely helpful to know which bugs were fixed and which features added.

Also remove the empty "Version history" from the manual.

Resolves #18

[olexandr-konovalov]

This PR is clearly good, but Travis tests fail in GAP 4.9: https://travis-ci.org/gap-packages/primgrp/jobs/579794706. I am afraid one can not claim compatibility with GAP 4.9 any more. Which is fine, since GAP 4.10.0 is November 2018, and 4.11 is on the horizon.

[fingolfin]

Tests on GAP 4.9 only fail because we now actually test on 4.9 -- I pushed the relevant Travis changes in 649926d0108b297d18a28d7a2cc23020371b27b2 directly to master -- which in retrospect of course was somewhat naive: I blindly trusted the information in PackageInfo.g :-).

Looking at the failing test, though, it seems to me that the problem on 4.9 really only is the test depending on the specific result of a computation in GAP >= 4.10; there is no actual fundamental issue, as far as I can tell:

...
########> Diff in /home/travis/build/gap-packages/primgrp/gaproot/pkg/primgrp/\
tst/testinstall/bugfix.tst:7
# Input is:
IsomorphismTypeInfoFiniteSimpleGroup(G);
# Expected output:
rec( name := "2F(4,2)' = Ree(2)' = Tits", parameter := 2, series := "2F", 
  shortname := "2F4(2)'" )
# But found:
rec( name := "2F(4,2)' = Ree(2)' = Tits", parameter := 2, series := "2F" )
########
########> Diff in /home/travis/build/gap-packages/primgrp/gaproot/pkg/primgrp/\
tst/testinstall/bugfix.tst:14
# Input is:
IsomorphismTypeInfoFiniteSimpleGroup(G);
# Expected output:
rec( name := "2F(4,2)' = Ree(2)' = Tits", parameter := 2, series := "2F", 
  shortname := "2F4(2)'" )
# But found:
rec( name := "2F(4,2)' = Ree(2)' = Tits", parameter := 2, series := "2F" )
########
########> Diff in /home/travis/build/gap-packages/primgrp/gaproot/pkg/primgrp/\
tst/testinstall/bugfix.tst:25
# Input is:
IsomorphismTypeInfoFiniteSimpleGroup(G);
# Expected output:
rec( name := "2F(4,2)' = Ree(2)' = Tits", parameter := 2, series := "2F", 
  shortname := "2F4(2)'" )
# But found:
rec( name := "2F(4,2)' = Ree(2)' = Tits", parameter := 2, series := "2F" )
########
     189 ms (58 ms GC) and 9.06MB allocated for bugfix.tst
...

Overall, I think that means this PR is safe to merge, the problem is elsewhere.

[olexandr-konovalov]

Sure the PR is ok. The problem is a hassle though, since now when the next Travis build fail you have always inspect test logs to see if there is anything else showing up.