added some basic tests of the core request() method using dropbox/responses
moved integration tests to new file
added docstrings for new tests and finished testing input arguments of request()
updated remaining tests in test_core.py and removed cursor test (which will be replaced)
skipping tests that were failing because of external dependency on Twitter
updated unit tests and travis config for python 2.6 and 3
python 3.3 workaround for dropbox/responses issue
requests returns content as bytes so use bytes for test strings. Also changed api verison in test 1.1 to not confuse people
Merge pull request #303 from cash/unit_tests

Fixes #297 New unit tests based on responses