Bugfix: charts with multiple exes, plus units for force constants

• Add units for force constants (kJ/mol/Å^2,...)
• Fixed an issue naming axes in plots with multiple axes

Added default units for viscosity and fixed a bug in handling dimensions

• Added more default units: dynamic viscosity (cP, etc) and kinematic viscosity (cSt, etc)
• Fixed a bug handling unit dimensions since the order changed in Pint. Now they are put in a standard alphabetical order.

Added configuration file handler

• Added a configuration file handler that preserves comments in the file so that documentation is not stripped.

Added temperature-energy conversions

• Added conversions from temperature units, like K, to energy, like kJ/mol and vice versa.
• Used more of the Pint contexts, which should allow wavenumbers to frequency, etc.

Added support for URI's for files

• Now recognize URI's in the form local:path/to/file
• An optional URI handler can be passed in to resolve such URI's.

Bugfix: Handling of duplicates in lists defined in the GUI

• Roundoff in floating point numbers caused some duplicates to be missed. The code now checks for duplicates in a more robust way. This affected lists in the GUI, such as the points in an Energy Scan step.

Added utility for handling list definitions

• Add list_definition.py with parse_list()
• Updated makefile for doctests.

Removed debug printing left accidentally

Merge pull request #55 from molssi-seamm/dev

Removed debug printing.

Moving user preferences to ~/.seamm.d

• To better support Docker, moving ~/.seammrc to ~/.seamm.d/seamrc
• Moved seamm.ini from ~/SEAMM to ~/seamm.d since it only contains personal preferences.

Internal update

• Versioneer needed to be updated to account for changes in configparser.