Remove redundant $CAN_HAZ_XS check

$CAN_HAZ_XS_PRED implies $CAN_HAZ_XS
Revert "Remove redundant $CAN_HAZ_XS check"

As @haarg pointed out, this isn't redundant because they are variables,
not constants.

This reverts commit 17e761a5fb4af3cdf71f15f9b3e9717b9918a007.
use dashes for travis perl build flags due to change in helpers
support for coerce => 1
documentation for coerce=>1
test coerce => 1 without Type::Tiny
also test coerce => 1 integration with Type::Tiny
Merge branch 'coerce-1'
put travis helpers in home dir
ignore failures to build on blead
improve Makefile.PL boilerplate
include perl version in metadata
minor refactor of isa/coerce wrapping with better names
use evals rather than a global __DIE__ override to handle accessor exceptions

Instead of overriding $SIG{__DIE__}, use an eval to add information
about the relevant accessors to errors during isa checks or coercions.
This prevents modifying messages of exceptions generated within the isa
check, which may not be related to the attribute itself.

Part of the implementation taken from work done by
Michael G. Schwern <schwern@pobox.com>.
test odd exception cases with accessors
Tests for eliminating global die handler
optimize better for isa case
changelog for using eval instead of __DIE__ to handle isa errors
Merge branch 'isa-eval'
consistently format has args as code in pod