Merge branch 'fix-travis'
use ? for unknown version in BinResolver::Bin#to_s
fix typo in BenResolver description
document few places in BinResolver
convert resolve? to resolve_bin returning instance of Bin
pass also full path to Bin initializer
extract BinResolver::Error to separate file, require in Worker
ensure Bin#name is a symbol
move bin version checking to BinResolver::Bin
move getting version to Bin
move/rename BinResolver::BadBinVersion to BinResolver::Bin::BadVersion
convert resolve_bin to symlink_custom_bin!, moving rest to resolve!
use `command -v` instead of getting version to check if bin is accessible
check custom bin to exist, be a file and be executable
use guard clause in symlink_custom_bin!
use path in Bin#to_s
fail if did not got version, resolves part of #39
document few more places in BinResolver
make version warnings bolder
fix Bin class doc comment