Travis CI purge old versions of memcached and libmemcached (#309)

* Purge all things memcached from Travis CI before installing local copies
* Add ancient libmemcached 1.0.2 to Travis CI matrix

Author: sodabrew

Diff for: .travis.yml

@@ -13,6 +13,7 @@ env:
     - LIBMEMCACHED_VERSION=1.0.18 # Debian Jessie / Ubuntu Xenial
     - LIBMEMCACHED_VERSION=1.0.16 # RHEL / CentOS 7
     - LIBMEMCACHED_VERSION=1.0.8  # Debian Wheezy / Ubuntu Trusty
+    - LIBMEMCACHED_VERSION=1.0.2  # Ancient
 
 addons:
     apt:
@@ -22,11 +23,12 @@ addons:
             - libevent-dev
 
 before_script:
+    - sudo apt-get purge -qq '^memcached*' '^libmemcached*'
     - ./.travis/travis.sh before_script $LIBMEMCACHED_VERSION
 
 script:
     - ./.travis/travis.sh script $LIBMEMCACHED_VERSION
 
 cache:
     directories: 
-    - $HOME/cache
+    - $HOME/cache