v0.6.3

ApproxFunBase v0.6.3

Diff since v0.6.2

Merged pull requests:

• remove unnecessary conversion to Any (#138) (@jishnub)
• Simplify union for spaces (#139) (@jishnub)
• Export inplace fwd/inv transform functions (#140) (@jishnub)
• Test transform using AFOP (#141) (@jishnub)
• Version bump to v0.6.3 (#143) (@jishnub)