MRG, MAINT: Better checks for int-ness

[larsoner]

Be more permissive of True/False in read_raw_edf, but also more strict in _validate_types since passing a bool to act as an int is much more likely to cause unexpected behaviors than expected ones (and easily worked around with int(my_bool) if people actually want to provide an int).

No need for latest.inc update I think since this is mostly an internal change (except maybe for being more permissive, but I'm not sure that's even worth advertising).

Closes #7485

[larsoner]

Travis failure is just the one fixed by #7501

[codecov]

Codecov Report

Merging #7500 into master will increase coverage by 0.00%.
The diff coverage is 88.23%.

@@           Coverage Diff           @@
##           master    #7500   +/-   ##
=======================================
  Coverage   90.12%   90.12%           
=======================================
  Files         453      453           
  Lines       82661    82675   +14     
  Branches    13052    13054    +2     
=======================================
+ Hits        74496    74512   +16     
+ Misses       5344     5343    -1     
+ Partials     2821     2820    -1     

[agramfort]

thx @larsoner