Fix cargo PATH, move meson to pip3
diff --git a/.travis.yml b/.travis.yml
index 5b17bb5..ee85349 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -10,10 +10,13 @@
       apt:
         packages:
           - nasm
-          - meson
           - ninja-build
+          - python3
+          - python3-pip
     before_script:
       - curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y
+      - pip3 install meson
+      - source $HOME/.cargo/env
       - cd ext
       - bash aom.cmd
       - bash dav1d.cmd
@@ -31,10 +34,13 @@
       apt:
         packages:
           - nasm
-          - meson
           - ninja-build
+          - python3
+          - python3-pip
     before_script:
       - curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y
+      - pip3 install meson
+      - source $HOME/.cargo/env
       - cd ext
       - bash aom.cmd
       - bash dav1d.cmd
@@ -52,10 +58,13 @@
       apt:
         packages:
           - nasm
-          - meson
           - ninja-build
+          - python3
+          - python3-pip
     before_script:
       - curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y
+      - pip3 install meson
+      - source $HOME/.cargo/env
       - cd ext
       - bash aom.cmd
       - bash dav1d.cmd
@@ -73,10 +82,13 @@
       apt:
         packages:
           - nasm
-          - meson
           - ninja-build
+          - python3
+          - python3-pip
     before_script:
       - curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y
+      - pip3 install meson
+      - source $HOME/.cargo/env
       - cd ext
       - bash aom.cmd
       - bash dav1d.cmd