v0.2.0

ExtXYZ v0.2.0

Diff since v0.1.14

Merged pull requests:

• initial attempt at resolving problems with round-tripping isolated systems (#48) (@jameskermode)
• Generalise system properties type check (#49) (@mfherbst)
• Make compatible with AtomsBase 0.4.x (#51) (@cortner)

Closed issues:

• Files with missing cell (#37)
• Read error (#44)
• Reading in frames from an IOBuffer (#46)
• Saving isolated molecules to a file results a file that cannot be read (#47)
• Update to AB0.4 (#50)