BUG: Fix problem with default basedir

If the base data directory was not set, a default one would be selected,
by using '..' to refer to a directory below, which in turn would
inconsistently flag users as lacking permissions:

```
QiitaPetAuthorizationError: User demo@microbio.me is not authorized to
access
/Users/yoshikivazquezbaeza/.virtualenvs/qiita-0.2.0-rc1/lib/python2.7/site-packages/qiita_db/support_files/test_data/job/1_summarize_taxa_through_plots.py_output_dir/taxa_summary_plots/bar_charts.html
```

Although the paths were the same, this is verified through string
matching thus 'lol/foo/../jk' and 'lol/jk' would not match (see example
structure below) even though they refer to the same folder:

lol/
├── foo
│   └── file.txt
├── jk
└── plel

Author: ElDeveloper

qiita_core/configuration_manager.py

@@ -144,8 +144,8 @@ def __init__(self):
     def _get_main(self, config):
         """Get the configuration of the main section"""
         self.test_environment = config.getboolean('main', 'TEST_ENVIRONMENT')
-        default_base_data_dir = join(dirname(abspath(__file__)),
-                                     '..', 'qiita_db', 'support_files',
+        install_dir = dirname(dirname(abspath(__file__)))
+        default_base_data_dir = join(install_dir, 'qiita_db', 'support_files',
                                      'test_data')
         self.base_data_dir = config.get('main', 'BASE_DATA_DIR') or \
             default_base_data_dir