Implement new releases

as per https://push-language.hampshire.edu/t/clojush-versioning/450/4?u=saulshanabrook

CONTRIBUTING.md

@@ -45,10 +45,11 @@ the [repository settings in Travis](http://docs.travis-ci.com/user/environment-v
 so that it can the release to Clojars. It also needs the `GITHUB_TOKEN`
 in order to push the added tag and commit back to Github.
 
-So Travis will:
+Travis will:
 
-1. Build docs + push those to `gh-pages` branch after every master branch build
-2. Run `lein release` as well on those builds. This will:
+1. Build docs + push those to `gh-pages` branch after every master branch build with the keyword `lein release $LEVEL`
+   For example, you could have a commit message like `add some stuff lein release :patch` which would cause it to do a patch release.
+2. Run `lein release $LEVEL` as well on those builds. This will:
     1. create new git commit and tag for new commit w/ out `-SNAPSHOT` in it
     2. Create jar and push that to clojars
     3. bump release number to next minor version

scripts/after_success.sh

@@ -9,6 +9,10 @@ set -o pipefail
 
 AUTOMATED_AUTHOR_EMAIL=_@_._
 AUTOMATED_AUTHOR_NAME=_
+LEIN_RELEASE_COMMAND="git log --format=%B --no-merges -n 1 | grep -o 'lein release :[a-z]*'"
+
+# exit if no lein release
+[ $LEIN_RELEASE_COMMAND ]
 
 git remote set-url origin https://$GITHUB_TOKEN@github.com/$TRAVIS_REPO_SLUG.git
 git branch --set-upstream-to origin/master master
@@ -22,4 +26,4 @@ git pull origin gh-pages
 ./scripts/deploy-docs.sh --verbose
 git checkout master
 git pull origin master
-lein release
+eval $LEIN_RELEASE_COMMAND