internal database package refactor: use composite pattern for managing commands
removed unused assignments and imports
CD matrix now updated, if present, when Map pixel size is changed.
Better pattern for checking for key existence in dictionaries
Merge pull request #1187 from ayshih/resample

CD matrix now updated, if present, when Map pixel size is changed.
Fix PC matrix calculation from CD matrix.

This fixes a bug with SWAP files.
Write some broken tests.
Fix CD matrix test and test file
fix database test numbers
Conflicts:
	sunpy/database/tests/test_tables.py
Merge pull request #1151 from derdon/pyflakes

removed unused assignments and imports
Merge pull request #1150 from derdon/dbcmds-refactor

internal database package refactor
Change the travis matrix so that most of the build are offline.
Only do coverage on the online build.
Remove Python 2.6 from the travis build
Find Python 2.6 references and remove them
Merge pull request #1190 from Cadair/travis_flip

Change the travis matrix so that most of the build are offline.
Merge pull request #1188 from Cadair/cd_matrix_fix

Cd matrix fix