Update waf to support Python 3

[himkt]

Ref: #155

Create waf with Python3.7 (Anaconda3-5.3.0)

[himkt]

Update unittest_gtest.py which is ported from tanakh/waf-unittest#18

[eiichiroi]

LGTM!

I have tested in python 2.7.5 (CentOS 7) and python 3.6.6 (CentOS 7 + EPEL).

Memo: Build scripts require bzip2 for unittest_gtest.py to unpack gtest's tar.bz2 file.

I catched the following error in the environment without bzip2.

$ ./waf configure
Setting top to                           : /Users/eiichiro/git/pficommon
Setting out to                           : /Users/eiichiro/git/pficommon/build
Checking for 'g++' (C++ compiler)        : /usr/bin/g++
tar (child): lbzip2: Cannot exec: No such file or directory
tar (child): Error is not recoverable: exiting now
tar: Child returned status 2
tar: Error is not recoverable: exiting now
gtest cannot be unpacked.
Unpacking gtest                          : no
[Errno 2] No such file or directory: 't.tar.bz2'
Checking for library pthread             : yes
Checking for library pthread             : yes
Checking for header msgpack.hpp          : not found
Checking for header fcgiapp.h            : not found
Checking for header stdint.h             : yes
Checking for header unordered_map        : not found
Checking for header tr1/unordered_map    : yes
Checking for header unordered_set        : not found
Checking for header tr1/unordered_set    : yes
Checking for ''                          : not found
Checking for ''                          : not found
...

[eiichiroi]

TODO: Update document: https://github.com/retrieva/pficommon/blob/master/doc/source/install.rst