Add pylint and its prereqs

I find pylint invaluable for my daily development, so here's my attempt at getting it working with conda. It works for Python 3.3 just fine, but with 2.7 conda crashes with the following issue:

```
compiling .pyc files...
Compiling /home/dblanchard/anaconda/envs/_build/lib/python2.7/site-packages/pylint/test/input/func_3k_removed_stuff_py_30.py ...
  File "/home/dblanchard/anaconda/envs/_build/lib/python2.7/site-packages/pylint/test/input/func_3k_removed_stuff_py_30.py", line 4
    from __future__ import generators
SyntaxError: from __future__ imports must occur at the beginning of the file

Compiling /home/dblanchard/anaconda/envs/_build/lib/python2.7/site-packages/pylint/test/input/func_continue_not_in_loop.py ...
  File "/home/dblanchard/anaconda/envs/_build/lib/python2.7/site-packages/pylint/test/input/func_continue_not_in_loop.py", line 8
    continue
SyntaxError: 'continue' not properly in loop

Compiling /home/dblanchard/anaconda/envs/_build/lib/python2.7/site-packages/pylint/test/input/func_e0108.py ...
SyntaxError: duplicate argument '_' in function definition (func_e0108.py, line 4)

Compiling /home/dblanchard/anaconda/envs/_build/lib/python2.7/site-packages/pylint/test/input/func_exec_used_py30.py ...
  File "/home/dblanchard/anaconda/envs/_build/lib/python2.7/site-packages/pylint/test/input/func_exec_used_py30.py", line 6
    exec('a = 1', globals={})
                         ^
SyntaxError: invalid syntax

Compiling /home/dblanchard/anaconda/envs/_build/lib/python2.7/site-packages/pylint/test/input/func_keyword_repeat.py ...
  File "/home/dblanchard/anaconda/envs/_build/lib/python2.7/site-packages/pylint/test/input/func_keyword_repeat.py", line 8
    function_default_arg(two=5, two=7)
SyntaxError: keyword argument repeated

Compiling /home/dblanchard/anaconda/envs/_build/lib/python2.7/site-packages/pylint/test/input/func_kwoa_py30.py ...
  File "/home/dblanchard/anaconda/envs/_build/lib/python2.7/site-packages/pylint/test/input/func_kwoa_py30.py", line 3
    def function(*, foo):
                  ^
SyntaxError: invalid syntax

Compiling /home/dblanchard/anaconda/envs/_build/lib/python2.7/site-packages/pylint/test/input/func_return_outside_func.py ...
  File "/home/dblanchard/anaconda/envs/_build/lib/python2.7/site-packages/pylint/test/input/func_return_outside_func.py", line 3
    return
SyntaxError: 'return' outside function

Compiling /home/dblanchard/anaconda/envs/_build/lib/python2.7/site-packages/pylint/test/input/func_return_yield_mix.py ...
SyntaxError: 'return' with argument inside generator (func_return_yield_mix.py, line 8)

Compiling /home/dblanchard/anaconda/envs/_build/lib/python2.7/site-packages/pylint/test/input/func_syntax_error.py ...
  File "/home/dblanchard/anaconda/envs/_build/lib/python2.7/site-packages/pylint/test/input/func_syntax_error.py", line 1
    def toto
           ^
SyntaxError: invalid syntax

Compiling /home/dblanchard/anaconda/envs/_build/lib/python2.7/site-packages/pylint/test/input/func_unknown_encoding.py ...
  File "/home/dblanchard/anaconda/envs/_build/lib/python2.7/site-packages/pylint/test/input/func_unknown_encoding.py", line 0
SyntaxError: unknown encoding: IBO-8859-1

Compiling /home/dblanchard/anaconda/envs/_build/lib/python2.7/site-packages/pylint/test/input/func_w0705.py ...
  File "/home/dblanchard/anaconda/envs/_build/lib/python2.7/site-packages/pylint/test/input/func_w0705.py", line 28
    __revision__ += 1
SyntaxError: default 'except:' must be last

Compiling /home/dblanchard/anaconda/envs/_build/lib/python2.7/site-packages/pylint/test/input/func_yield_outside_func.py ...
  File "/home/dblanchard/anaconda/envs/_build/lib/python2.7/site-packages/pylint/test/input/func_yield_outside_func.py", line 3
    yield 1
SyntaxError: 'yield' outside function

Compiling /home/dblanchard/anaconda/envs/_build/lib/python2.7/site-packages/pylint/test/input/syntax_error.py ...
Sorry: IndentationError: expected an indented block (syntax_error.py, line 2)
An unexpected error has occurred, please consider sending the
following traceback to the conda GitHub issue tracker at:

    https://github.com/ContinuumIO/conda/issues

Include the output of the command 'conda info' in your report.


Traceback (most recent call last):
  File "/home/dblanchard/anaconda/bin/conda", line 5, in <module>
    sys.exit(main())
  File "/home/dblanchard/anaconda/lib/python2.7/site-packages/conda/cli/main.py", line 183, in main
    args.func(args, p)
  File "/home/dblanchard/anaconda/lib/python2.7/site-packages/conda/cli/main_build.py", line 169, in execute
    build.build(m, pypi=args.pypi)
  File "/home/dblanchard/anaconda/lib/python2.7/site-packages/conda/builder/build.py", line 176, in build
    post_process()
  File "/home/dblanchard/anaconda/lib/python2.7/site-packages/conda/builder/post.py", line 107, in post_process
    compile_missing_pyc()
  File "/home/dblanchard/anaconda/lib/python2.7/site-packages/conda/builder/post.py", line 100, in compile_missing_pyc
    '-q', '-x', 'port_v3', sp_dir])
  File "/home/dblanchard/anaconda/lib/python2.7/subprocess.py", line 540, in check_call
    raise CalledProcessError(retcode, cmd)
subprocess.CalledProcessError: Command '['/home/dblanchard/anaconda/envs/_build/bin/python', '-Wi', '/home/dblanchard/anaconda/envs/_build/lib/python2.7/compileall.py', '-q', '-x', 'port_v3', '/home/dblanchard/anaconda/envs/_build/lib/python2.7/site-packages']' returned non-zero exit status 1
```

I believe the issue is that conda is trying to compile all `.py` files, including those that are tests for pylint (i.e., it needs input with incorrect syntax to check its own syntax checker). Is there a way to exclude certain files from compilation?