update .travis.yml: tweak indent in install script

.travis.yml

@@ -5,13 +5,13 @@ sudo: false
 install:
   - git clone --depth=1 https://github.com/thinca/vim-themis /tmp/themis
   - (if ! test -d $HOME/vim-$VIM_VERSION/bin; then
-      git clone https://github.com/vim/vim $HOME/vim &&
-      cd $HOME/vim &&
-      git checkout v$VIM_VERSION &&
-      ./configure --prefix=$HOME/vim-$VIM_VERSION &&
-      make &&
-      make install;
-    fi)
+       git clone https://github.com/vim/vim $HOME/vim &&
+       cd $HOME/vim &&
+       git checkout v$VIM_VERSION &&
+       ./configure --prefix=$HOME/vim-$VIM_VERSION &&
+       make &&
+       make install;
+     fi)
 
 cache:
   directories: