enable cpplint, remove go_fmt

[luotao1]

• enable cpplint on travis_ci
• remove paddle/scripts/cpplint.py, we use pip install cpplint on both local machine and travis_ci
• remove go_fmt since fluid version doesn't have go codes

TODO: cpplint on travis_ci runs in multi-thread, and it will print several same logs when there are errors.
related #15907 #15876

[luotao1]

28680c6 will report the cpplint error:

Done processing paddle/scripts/paddle_build.sh
Done processing tools/codestyle/cpplint_pre_commit.hook
Ignoring .pre-commit-config.yaml; not a valid file name (c, cc, h, hpp, c++, h++, hh, cu, cpp, hxx, cxx, cuh)
paddle/fluid/framework/async_executor.h:90:  Add #include <string> for string  [build/include_what_you_use] [4]

https://travis-ci.org/PaddlePaddle/Paddle/builds/498684394#L881

[luotao1]

@panyx0718 Could you help approve for the const_cast in the removed file cpplint.py?

[13:46:44][Step 1/1] + HAS_CONST_CAST=const_cast
[13:46:44][Step 1/1] + '[' const_cast ']'
[13:46:44][Step 1/1] + '[' 15939 '!=' '' ']'
[13:46:44][Step 1/1] ++ curl -H 'Authorization: token 95a329e820eeae12c4c5c8a0b6e3e39654dc01a4' 'https://api.github.com/repos/PaddlePaddle/Paddle/pulls/15939/reviews?per_page=10000'
[13:46:44][Step 1/1] ++ python /paddle/tools/check_pr_approval.py 1 2887803
[13:46:44][Step 1/1]   % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
[13:46:44][Step 1/1]                                  Dload  Upload   Total   Spent    Left  Speed
[13:46:44][Step 1/1] 
[13:46:45][Step 1/1]   0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0
[13:46:46][Step 1/1]   0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0
[13:46:46][Step 1/1]   0     0    0     0    0     0      0      0 --:--:--  0:00:01 --:--:--     0
[13:46:46][Step 1/1] 100     5  100     5    0     0      3      0  0:00:01  0:00:01 --:--:--     3
[13:46:46][Step 1/1] + APPROVALS=FALSE
[13:46:46][Step 1/1] current pr 15939 got approvals: FALSE
[13:46:46][Step 1/1] + echo 'current pr 15939 got approvals: FALSE'