use boost 1.56 in travis build

.travis.yml

@@ -5,11 +5,12 @@ dist: trusty
 addons:
   apt:
     sources:
+      - boost-latest
       - ubuntu-toolchain-r-test
     packages:
       - gcc-5
       - g++-5
-      - libboost-all-dev
+      - libboost1.56-all-dev
       - cmake
 
 env:

README.md

@@ -18,8 +18,8 @@ Precise map-matching for public transit schedules (GTFS data).
 ## Requirements
 
  * `cmake`
- * `gcc`
- * `libboost-system`, `libboost-filesystem`, `libboost-geometry`
+ * `gcc` >= 5
+ * `libboost-system` >= 1.56, `libboost-filesystem` >= 1.56, `libboost-geometry` >= 1.56
 
 ## Building and Installation