try to fix travis, pbc should compile standalone

.travis.yml

@@ -8,16 +8,5 @@ otp_release:
 cache:
   directories:
   - $HOME/.cache/rebar3
-  - $HOME/.cache/pbc
 
-before_script:
-    kerl list installations &&
-    git clone https://github.com/blynn/pbc &&
-    cd pbc &&
-    autoreconf -fvi &&
-    ./configure --prefix $HOME/.cache/pbc &&
-    make &&
-    make install &&
-    cd ..
-
-script: CFLAGS="-I $HOME/.cache/pbc/include" LDFLAGS="-L$HOME/.cache/pbc/lib" LD_LIBRARY_PATH="$HOME/.cache/pbc/lib" ./rebar3 as test do ct && ./rebar3 dialyzer && ./rebar3 coveralls send
+script: ./rebar3 as test do ct && ./rebar3 dialyzer && ./rebar3 coveralls send