Merge pull request #208 from baev/1.3.7

add allure version
[maven-release-plugin] prepare release allure-core-1.3.7
[maven-release-plugin] prepare for next development iteration
rft - pretty btns for stacktrace in testcases
Merge pull request #209 from allure-framework/btns

rft - pretty btns for stacktrace in testcases
add remove attachments event
add info about listener
add sha256 util
change attachments naming strategy from UUID to sha256
remove unused test
add hash generator test
don't write file if already exists
add attachment save and delete test
add ability to delete attachments by name regex