Move 'runtests' out of the package root directory

Running the test suite out of 'tests/' prevents adding the package root
to 'sys.path', which would cause the local 'rest_framework' files to
conflict with the installed package/distribution.

Author: Ryan P Kilby

runtests.py renamed to tests/runtests.py

@@ -14,7 +14,7 @@ DJANGO =
     master: djangomaster
 
 [testenv]
-commands = ./runtests.py --fast --coverage {posargs}
+commands = python tests/runtests.py --fast --coverage {posargs}
 envdir = {toxworkdir}/venvs/{envname}
 setenv =
        PYTHONDONTWRITEBYTECODE=1
@@ -34,15 +34,15 @@ deps =
         -rrequirements/requirements-testing.txt
 
 [testenv:dist]
-commands = ./runtests.py --fast --no-pkgroot --staticfiles {posargs}
+commands = python tests/runtests.py --fast --no-pkgroot --staticfiles {posargs}
 deps =
         django
         -rrequirements/requirements-testing.txt
         -rrequirements/requirements-optionals.txt
 
 [testenv:lint]
 basepython = python2.7
-commands = ./runtests.py --lintonly
+commands = python tests/runtests.py --lintonly
 deps =
         -rrequirements/requirements-codestyle.txt
         -rrequirements/requirements-testing.txt