Merge pull request #6870 from typhoonzero/fix_cmake_req_doc

fix cmake require docs

doc/getstarted/build_and_install/build_from_source_cn.rst

@@ -70,13 +70,13 @@ PaddlePaddle编译需要使用到下面的依赖（包含但不限于），其
    :header: "依赖", "版本", "说明"
    :widths: 10, 15, 30
 
-   "CMake", ">=3.5", ""
+   "CMake", ">=3.2", ""
    "GCC", "4.8.2", "推荐使用CentOS的devtools2"
-   "Python", "2.7.x", "依赖libpython2.7.so"
-   "pip", ">=9.0", ""
-   "numpy", "", ""
+   "Python", "2.7.x", "依赖libpython2.7.so"
+   "pip", ">=9.0", ""
+   "numpy", "", ""
    "SWIG", ">=2.0", ""
-   "Go", ">=1.8", "可选"
+   "Go", ">=1.8", "可选"
 
 
 .. _build_options:

doc/getstarted/build_and_install/build_from_source_en.rst

@@ -76,13 +76,13 @@ will be downloaded automatically.
    :header: "Dependency", "Version", "Description"
    :widths: 10, 15, 30
 
-   "CMake", ">=3.5", ""
+   "CMake", ">=3.2", ""
    "GCC", "4.8.2", "Recommend devtools2 for CentOS"
-   "Python", "2.7.x", "Need libpython2.7.so"
-   "pip", ">=9.0", ""
-   "numpy", "", ""
+   "Python", "2.7.x", "Need libpython2.7.so"
+   "pip", ">=9.0", ""
+   "numpy", "", ""
    "SWIG", ">=2.0", ""
-   "Go", ">=1.8", "Optional"
+   "Go", ">=1.8", "Optional"
 
 
 .. _build_options: