THRIFT-3696 Install pip to CentOS Docker images to fix Python builds

This closes #912
diff --git a/.travis.yml b/.travis.yml
index 6b99965..10da1f9 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -110,14 +110,14 @@
       BUILD_ARG="-DCMAKE_TOOLCHAIN_FILE=../build/cmake/mingw32-toolchain.cmake -DBUILD_COMPILER=ON -DBUILD_LIBRARIES=OFF -DBUILD_TESTING=OFF -DBUILD_EXAMPLES=OFF"
       BUILD_ENV=""
 
-    - TEST_NAME="All (CentOS)"
+    - TEST_NAME="All - GCC (CentOS)"
       BUILD_CMD="../cmake.sh"
+      BUILD_ENV="-e CC=gcc -e CXX=g++"
       DISTRO=centos
 
-    - TEST_NAME="C C++ - GCC (CentOS)"
+    - TEST_NAME="C C++ - Clang (CentOS)"
       BUILD_CMD="../cmake.sh"
       BUILD_ARG="-DWITH_PYTHON=OFF -DWITH_JAVA=OFF -DWITH_HASKELL=OFF"
-      BUILD_ENV="-e CC=gcc -e CXX=g++"
       DISTRO=centos
 
     - TEST_NAME="Python 2.6 (CentOS 6)"
diff --git a/build/docker/centos/Dockerfile b/build/docker/centos/Dockerfile
index 4ce4f42..011ccc0 100644
--- a/build/docker/centos/Dockerfile
+++ b/build/docker/centos/Dockerfile
@@ -58,7 +58,7 @@
       python-devel \
       python-setuptools \
       python-twisted-web \
-      python-six
+      python-pip
 
 # Ruby Dependencies
 RUN yum install -y \
diff --git a/build/docker/centos6/Dockerfile b/build/docker/centos6/Dockerfile
index 0e571c5..33d5dad 100644
--- a/build/docker/centos6/Dockerfile
+++ b/build/docker/centos6/Dockerfile
@@ -19,7 +19,8 @@
 FROM centos:6
 MAINTAINER Apache Thrift <dev@thrift.apache.org>
 
-RUN yum install -y \
+RUN yum install -y epel-release && \
+    yum install -y \
       autoconf \
       bison \
       bison-devel \
@@ -36,7 +37,7 @@
       python-devel \
       python-setuptools \
       python-twisted-web \
-      python-six \
+      python-pip \
     && yum clean all
 
 # CMake
diff --git a/build/docker/debian/Dockerfile b/build/docker/debian/Dockerfile
index b6cf4fb..a85d9e1 100644
--- a/build/docker/debian/Dockerfile
+++ b/build/docker/debian/Dockerfile
@@ -55,7 +55,7 @@
     && update-java-alternatives -s java-1.7.0-openjdk-amd64
 
 # Python dependencies
-RUN apt-get update && apt-get install -y \
+RUN apt-get update && apt-get install -y --no-install-recommends \
       python-all \
       python-all-dev \
       python-all-dbg \
@@ -64,6 +64,7 @@
       python-twisted \
       python-zope.interface \
       python-pip \
+      python3-dev \
       python3-pip
 
 # Ruby dependencies
diff --git a/build/docker/ubuntu/Dockerfile b/build/docker/ubuntu/Dockerfile
index 44ad147..5180fca 100644
--- a/build/docker/ubuntu/Dockerfile
+++ b/build/docker/ubuntu/Dockerfile
@@ -55,15 +55,16 @@
     && update-java-alternatives -s java-1.7.0-openjdk-amd64
 
 # Python dependencies
-RUN apt-get update && apt-get install -y \
+RUN apt-get update && apt-get install -y --no-install-recommends \
       python-all \
-      python-all-dev \
       python-all-dbg \
+      python-all-dev \
+      python-pip \
       python-setuptools \
       python-support \
       python-twisted \
       python-zope.interface \
-      python-pip \
+      python3-dev \
       python3-pip
 
 # Ruby dependencies