v0.4.2

MITgcm v0.4.2

Diff since v0.4.1

• documentation improvements
• system_check
• default_path
• fixes

Merged pull requests:

• V0p4p2a (#112) (@gaelforget)
• V0p4p2b (#113) (@gaelforget)
• V0p4p2c (#114) (@gaelforget)
• docs improvements (#115) (@gaelforget)
• V0p4p2d (#116) (@gaelforget)