Add SLR(simple linear regression) analysis on report

[Bojun-Seo]

I suggest to add SLR analysis on report. SLR could help users to understand the trend of the memory allocation for each location(stack id). The trend denotes slope and r square. slope means the amount of usage(count or size) increasing as time goes, and r square means the similarity(1: very similar, 0: not similar). See details for more information.
https://online.stat.psu.edu/stat462/node/79/

I add pseudo SLR analysis result in the report below right after the age. The original contents come from README.md file.

$ heaptrace --top 3 --sort count /usr/bin/node --expose-gc -e 'gc()'
[heaptrace] initialized for /proc/5879/maps
[heaptrace] finalized for /proc/5879/maps
=================================================================
[heaptrace] dump allocation status for /proc/5879/maps (node)
=== backtrace #1 === [count/peak: 43/60] [size/peak: 22.704 KB/31.680 KB] [age: 6.236 ms] [slope: 0.11 KB/s] [r_square: 0.84]
 0 [0x7fe72e46476c] malloc +0x1b
 1 [0x7fe72dd61e78] operator new(unsigned long) +0x6
 2 [      0xf27811] /usr/bin/node (+0xf27811)
 3 [      0xf2e57d] v8::internal::MarkCompactCollector::RootMarkingVisitor::VisitRootPointer(v8::internal::Root, char const*, v8::internal::Objec... +0x1b
 4 [     0x121c32d] v8::internal::SerializerDeserializer::Iterate(v8::internal::Isolate*, v8::internal::RootVisitor*) +0x47
 5 [      0xf07e45] v8::internal::Heap::IterateStrongRoots(v8::internal::RootVisitor*, v8::internal::VisitMode) +0x91
 6 [      0xf40b6b] v8::internal::MarkCompactCollector::MarkLiveObjects() +0x72
 7 [      0xf42071] v8::internal::MarkCompactCollector::CollectGarbage() +0x4

=== backtrace #2 === [count/peak: 12/13] [size/peak: 6.336 KB/6.864 KB] [age: 6.400 ms] [slope: 0.53 KB/s] [r_square: 0.24]
 0 [0x7fe72e46476c] malloc +0x1b
 1 [0x7fe72dd61e78] operator new(unsigned long) +0x6
 2 [      0xf27811] /usr/bin/node (+0xf27811)
 3 [      0xf29dd4] v8::internal::MarkCompactCollector::RootMarkingVisitor::VisitRootPointers(v8::internal::Root, char const*, v8::internal::Obje... +0x29
 4 [      0xb27068] v8::internal::HandleScopeImplementer::IterateThis(v8::internal::RootVisitor*) +0x1e
 5 [      0xf07d33] v8::internal::Heap::IterateStrongRoots(v8::internal::RootVisitor*, v8::internal::VisitMode) +0x4c
 6 [      0xf40b6b] v8::internal::MarkCompactCollector::MarkLiveObjects() +0x72
 7 [      0xf42071] v8::internal::MarkCompactCollector::CollectGarbage() +0x4

=== backtrace #3 === [count/peak: 10/10] [size/peak: 5.280 KB/5.280 KB] [age: 6.322 ms] [slope: 0.04 KB/s] [r_square: 0.99]
 0 [0x7fe72e46476c] malloc +0x1b
 1 [0x7fe72dd61e78] operator new(unsigned long) +0x6
 2 [      0xf27811] /usr/bin/node (+0xf27811)
 3 [      0xf2e57d] v8::internal::MarkCompactCollector::RootMarkingVisitor::VisitRootPointer(v8::internal::Root, char const*, v8::internal::Objec... +0x1b
 4 [      0xf07f08] v8::internal::Heap::IterateStrongRoots(v8::internal::RootVisitor*, v8::internal::VisitMode) +0xc2
 5 [      0xf40b6b] v8::internal::MarkCompactCollector::MarkLiveObjects() +0x72
 6 [      0xf42071] v8::internal::MarkCompactCollector::CollectGarbage() +0x4
 7 [      0xf15621] v8::internal::Heap::MarkCompact() +0x28

[heaptrace] heap traced num of backtrace : 64
[heaptrace] heap traced allocation size  : 59.215 KB
[heaptrace] allocator info (virtual)     : 2.121 MB
[heaptrace] allocator info (resident)    : 414.288 KB
[heaptrace] statm info (VSS/RSS/shared)  : 134.201 MB / 40.960 KB / 0 bytes