`getTissueType` function does not vectorize correctly

[katehoffshutta]

MWE:

> my_friend$getTissueType("TCGA-AA-3552-01A")$description
[1] "Primary Solid Tumor"
> my_friend$getTissueType("TCGA-AA-3971-10A")$description
[1] "Blood Derived Normal"
> my_friend$getTissueType(c("TCGA-AA-3552-01A","TCGA-AA-3971-10A"))$description
[1] "Primary Solid Tumor" "Primary Solid Tumor"

[katehoffshutta]

Fixed in #67. The MWE above now yields:

> my_friend$getTissueType("TCGA-AA-3552-01A")$description
[1] "Primary Solid Tumor"
> my_friend$getTissueType("TCGA-AA-3971-10A")$description
[1] "Blood Derived Normal"
> my_friend$getTissueType(c("TCGA-AA-3552-01A","TCGA-AA-3971-10A"))$description
[1] "Primary Solid Tumor"  "Blood Derived Normal"

The unit test has also been fixed to catch this type of bug in the future.