v0.6.2

Devito v0.6.2

Diff since v0.6.1

Merged pull requests:

• create abstract subdomain type (#132) (@deckerla)
• making functions from pyobjects (#134) (@deckerla)
• adding support for symbolics (#135) (@deckerla)
• ensure Functions and SparseTimeFunctions created from (#136) (@deckerla)
• move method descriptions to appropriate place (#137) (@deckerla)
• indexed function support (#138) (@deckerla)
• restrict pycall to 1.93 (#139) (@deckerla)