Getting Bash-it to use the vendored composure

Fixed tests
Fixed install.sh and bash_it.sh
Added gitattributes to the vendor folder
Changed documentation

test/themes/base.theme.git.bats

@@ -1,7 +1,7 @@
 #!/usr/bin/env bats
 
 load ../test_helper
-load ../../lib/composure
+load "${BASH_IT}/vendor/github.com/erichs/composure/composure.sh"
 load ../../lib/log
 
 cite _about _param _example _group _author _version