bug fix about pypandoc dependency

README.md

@@ -64,7 +64,6 @@ Dependencies:
 + (optional) use tcmalloc if running with large data
 
 ```
-git clone https://github.com/ppwwyyxx/tensorpack/ && cd tensorpack
-pip install --user --upgrade .
+pip install --user -U git+https://github.com/ppwwyyxx/tensorpack.git
 pip install --user -r opt-requirements.txt # (some optional dependencies required by certain submodules, you can install later if prompted)
 ```

setup.py

@@ -14,7 +14,6 @@ try:
     import pypandoc
     long_description = pypandoc.convert_file('README.md', 'rst')
 except ImportError:
-    raise
     long_description = open('README.md').read()
 
 # configure requirements