I also run into problem with installation. It's having trouble finding ‘latticeGrob’ in gridExtra' even though I have downloaded maverick package and installed separately. 

EDIT: Turns out gridExtra v2.0.0 doesn't export latticeGrob anymore. it's only available in v.0.9.1. I rollback to gridExtra 0.9.1 and i can install now.

> library(SomaticSignatures)
Loading required package: VariantAnnotation
Loading required package: BiocGenerics
Loading required package: parallel

Attaching package: ‘BiocGenerics’

The following objects are masked from ‘package:parallel’:

    clusterApply, clusterApplyLB, clusterCall, clusterEvalQ, clusterExport, clusterMap, parApply, parCapply, parLapply,
    parLapplyLB, parRapply, parSapply, parSapplyLB

The following object is masked from ‘package:stats’:

    xtabs

The following objects are masked from ‘package:base’:

    anyDuplicated, append, as.data.frame, as.vector, cbind, colnames, do.call, duplicated, eval, evalq, Filter, Find,
    get, intersect, is.unsorted, lapply, Map, mapply, match, mget, order, paste, pmax, pmax.int, pmin, pmin.int,
    Position, rank, rbind, Reduce, rep.int, rownames, sapply, setdiff, sort, table, tapply, union, unique, unlist,
    unsplit

Loading required package: GenomeInfoDb
Loading required package: stats4
Loading required package: S4Vectors
Loading required package: IRanges
Loading required package: GenomicRanges
Loading required package: Rsamtools
Loading required package: XVector
Loading required package: Biostrings

Attaching package: ‘VariantAnnotation’

The following object is masked from ‘package:base’:

    tabulate

Error : object ‘latticeGrob’ is not exported by 'namespace:gridExtra'
Error: package or namespace load failed for ‘SomaticSignatures’
> library(gridExtra)
> sessionInfo()
R version 3.2.1 (2015-06-18)
Platform: x86_64-apple-darwin13.4.0 (64-bit)
Running under: OS X 10.9.5 (Mavericks)

locale:
[1] en_US.UTF-8/en_US.UTF-8/en_US.UTF-8/C/en_US.UTF-8/en_US.UTF-8

attached base packages:
[1] stats4    parallel  stats     graphics  grDevices utils     datasets  methods   base     

other attached packages:
 [1] gridExtra_2.0.0                VariantAnnotation_1.14.6       Rsamtools_1.20.4               Biostrings_2.36.1             
 [5] XVector_0.8.0                  GenomicRanges_1.20.5           GenomeInfoDb_1.4.1             IRanges_2.2.5                 
 [9] S4Vectors_0.6.1                BiocGenerics_0.14.0            SomaticCancerAlterations_1.4.0 BiocInstaller_1.18.3          

loaded via a namespace (and not attached):
 [1] Rcpp_0.11.6             futile.logger_1.4.1     plyr_1.8.3              GenomicFeatures_1.20.1  bitops_1.0-6           
 [6] futile.options_1.0.0    tools_3.2.1             zlibbioc_1.14.0         biomaRt_2.24.0          digest_0.6.8           
[11] RSQLite_1.0.0           gtable_0.1.2            BSgenome_1.36.2         GGally_0.5.0            DBI_0.3.1              
[16] proto_0.3-10            rtracklayer_1.28.6      stringr_1.0.0           grid_3.2.1              reshape_0.8.5          
[21] Biobase_2.28.0          exomeCopy_1.14.0        AnnotationDbi_1.30.1    XML_3.98-1.3            BiocParallel_1.2.9     
[26] ggplot2_1.0.1           reshape2_1.4.1          lambda.r_1.1.7          magrittr_1.5            MASS_7.3-42            
[31] scales_0.2.5            GenomicAlignments_1.4.1 colorspace_1.2-6        stringi_0.5-5           munsell_0.4.2          
[36] RCurl_1.95-4.7