Build the default database path from STORAGE_DIR

Currently, the default database path is hardcoded to /opt.  In a
development installation, graphite-web may be installed anywhere
and will fail to start following the development installation
instructions.  Using STORAGE_DIR aligns this value with the
comments earlier in the file.

- Changed definition of DATABASES

- Moved DATABASES definition to after STORAGE_DIR definition.
Don't overwrite local_settings.py defined DATABASES

As per the discussion in PR #937.
Fixing release notes after #941
Merge pull request #943 from deniszh/master_release_notes

Fixing release notes after #941
Merge pull request #937 from andrewbaxter/settings_default_db_path

Build the default database path from STORAGE_DIR
Fixing caching issue similar to #467 but for rendered graphs.
See https://github.com/graphite-project/graphite-web/pull/945#issuecomment-54818928
Merge pull request #947 from deniszh/master_rendered_cache_fix

Fixing caching issue similar to #467 but for rendered graphs.
generate the temporary directories from python
remove mkdir calls in travis config
Merge pull request #952 from esc/test/generate_temp_dir_python

generate temporary test directories from python
Log all exceptions

Uses a middleware to capture exceptions and log them.  This is useful
for serving images and ajax calls, where the text of 500 errors
are not displayed.
Merge branch 'master' into log_all_exceptions
Fixed whitespace.
Move middleware setting, improve exception message.
Removed unused import
Merge pull request #954 from andrewbaxter/log_all_exceptions

Log all exceptions
Rebase/fixing PR #416 ("Allow asPercent to take two series and match them together ") and #447 ("add function divideEachSeries") to master branch.
Documentation for divideEachSeries was added.