Add more specs

[oshikiri]

• refactored AllDSLSpec.scala
• fixed example-specs/github_punchcard.vl.json
• added more specs to AllDSLSpec.scala

ref https://github.com/vegas-viz/Vegas/issues/65

[codecov-io]

Codecov Report

Merging #133 into master will not change coverage. The diff coverage is 0%.

@@          Coverage Diff          @@
##           master   #133   +/-   ##
=====================================
  Coverage       0%     0%           
=====================================
  Files          27     27           
  Lines        1780   1783    +3     
  Branches        6      5    -1     
=====================================
- Misses       1780   1783    +3

Impacted Files	Coverage Δ
core/src/main/scala/vegas/data/External.scala	0% <0%> (ø)	:arrow_up:

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[dbtsai]

LGTM. Thanks.