update version to R15
optimize getServerVars

- fix "Too broad exception clause"
- some style fixes
- more debug/error output
handle broken admin.yell
Merge pull request #132 from ozon/improvements/BF4_parser

[BF4] update for R15 and parser improvements
create some exception for server responses

- raise CommandDisallowedError if the response is 'CommandDisallowedOnRanked' or 'CommandDisallowedOnOfficial'
- raise CommandUnknownCommandError if the response is 'UnknownCommand'
improve getServerVars and get getCvar
update version to R17
add cvar vars.ticketBleedRate

This value controls the rate of which tickets drop when the majority of control points
are held by a team (100% = normal).
Merge pull request #134 from ozon/improvements/BF4_parser

[BF4] Improvements bf4 parser