Further tweak of the travis build

- use leiningen 2.7.1
- use `lein` alias instead of `lein2`

Author: Benedek Fazekas

.travis.yml

@@ -1,10 +1,10 @@
 language: clojure
-lein: 2.6.1
+lein: 2.7.1
 script:
-  - lein2 source-deps :prefix-exclusions "[\"classlojure\"]"
-  - lein2 with-profile +plugin.mranderson/config test
-  - lein2 with-profile +1.8,+plugin.mranderson/config test
-  - lein2 with-profile +1.9,+plugin.mranderson/config test
+  - lein source-deps :prefix-exclusions "[\"classlojure\"]"
+  - lein with-profile +plugin.mranderson/config test
+  - lein with-profile +1.8,+plugin.mranderson/config test
+  - lein with-profile +1.9,+plugin.mranderson/config test
 jdk:
   - openjdk7
   - oraclejdk7